The Bw4 public epitope of HLA-B molecules confers reactivity with natural killer cell clones that express NKB1, a putative HLA receptor

High-resolution KIR and HLA genotyping in three Chinese ethnic minorities reveals distinct origins

Polymorphism of killer-cell immunoglobulin-like receptors (KIRs) and their HLA class I ligands impacts the effector activity of cytotoxic NK cell and T cell subsets. Therefore, understanding the extent and implications of KIR and HLA class I genetic polymorphism across various populations is important for immunological and medical research. In this study, we conducted a high-resolution investigation of KIR and HLA class I diversity in three distinct Chinese ethnic minority populations. We studied the She, Yugur, and Tajik, and compared them with the Zhejiang Han population (Zhe), which represents the majority Southern Han ethnicity. Our findings revealed that the Tajik population exhibited the most diverse KIR copy number, allele, and haplotype diversity among the four populations. This diversity aligns with their proposed ancestral origin, closely resembling that of Iranian populations, with a relatively higher presence of KIR-B genes, alleles, and haplotypes compared with the other Chinese populations. The Yugur population displayed KIR distributions similar to those of the Tibetans and Southeast Asians, whereas the She population resembled the Zhe and other East Asians, as confirmed by genetic distance analysis of KIR. Additionally, we identified 12.9% of individuals across the three minority populations as having KIR haplotypes characterized by specific gene block insertions or deletions. Genetic analysis based on HLA alleles yielded consistent results, even though there were extensive variations in HLA alleles. The observed variations in KIR interactions, such as higher numbers of 2DL1-C2 interactions in Tajik and Yugur populations and of 2DL3-C1 interactions in the She population, are likely shaped by demographic and evolutionary mechanisms specific to their local environments. Overall, our findings offer valuable insights into the distribution of KIR and HLA diversity among three distinct Chinese ethnic minority populations, which can inform future clinical and population studies.

Exceptional diversity of KIR and HLA class I in Egypt

Genetically determined variation of killer cell immunoglobulin like receptors (KIR) and their HLA class I ligands affects multiple aspects of human health. Their extreme diversity is generated through complex interplay of natural selection for pathogen resistance and reproductive health, combined with demographic structure and dispersal. Despite significant importance to multiple health conditions of differential effect across populations, the nature and extent of immunogenetic diversity is under-studied for many geographic regions. Here, we describe the first high-resolution analysis of KIR and HLA class I combinatorial diversity in Northern Africa. Analysis of 125 healthy unrelated individuals from Cairo in Egypt yielded 186 KIR alleles arranged in 146 distinct centromeric and 79 distinct telomeric haplotypes. The most frequent haplotypes observed were KIR-A, encoding two inhibitory receptors specific for HLA-C, two that are specific for HLA-A and -B, and no activating receptors. Together with 141 alleles of HLA class I, 75 of which encode a KIR ligand, we identified a mean of six distinct interacting pairs of inhibitory KIR and HLA allotypes per individual. We additionally characterize 16 KIR alleles newly identified in the study population. Our findings place Egyptians as one of the most highly diverse populations worldwide, with important implications for transplant matching and studies of immune-mediated diseases.

HLA-B*44 and the Bw4-80T motif are associated with poor outcome of relapse-preventive immunotherapy in acute myeloid leukemia

HLA-B alleles are associated with outcomes in various pathologies, including autoimmune diseases and malignancies. The encoded HLA-B proteins are pivotal in antigen presentation to cytotoxic T cells, and some variants containing a Bw4 motif also serve as ligands to the killer immunoglobulin-like receptors (KIR) 3DL1/S1 of NK cells. We investigated the potential impact of HLA-B genotypes on the efficacy of immunotherapy for relapse prevention in acute myeloid leukemia (AML). Seventy-eight non-transplanted AML patients receiving HDC/IL-2 in the post-consolidation phase were genotyped for HLA-B and KIR genes. HLA-B*44 heralded impaired LFS (leukemia-free survival) and overall survival (OS), but the negative association with outcome was not shared across alleles of the HLA-B44 supertype. Notably, HLA-B*44 is one of few HLA-B44 supertype alleles containing a Bw4 motif with a threonine at position 80, which typically results in weak binding to the inhibitory NK receptor, KIR3DL1. Accordingly, a strong interaction between KIR3DL1 and Bw4 was associated with superior LFS and OS (p = 0.014 and p = 0.027, respectively). KIR3DL1+ NK cells from 80 T-Bw4 donors showed significantly lower degranulation responses and cytokine responses than NK cells from 80I-Bw4 donors, suggesting impaired KIR3DL1-mediated education in 80 T-Bw4 subjects. We propose that presence of a strong KIR3DL1+-Bw4 interaction improves NK cell education and thus is advantageous in AML patients receiving HDC/IL-2 immunotherapy for relapse prevention.

Role of the Killer Immunoglobulin-like Receptor and Human Leukocyte Antigen I Complex Polymorphisms in Kaposi Sarcoma-Associated Herpesvirus Infection

Background

Kaposi sarcoma, caused by the pathogen Kaposi sarcoma-associated herpesvirus (KSHV), is the most common neoplasm for patients with AIDS. Susceptibility to KSHV has been associated with several different genetic risk variants. The purpose of this study was to test whether variants of killer cell immunoglobulin-like receptors (KIRs) and their human leukocyte antigen (HLA-I) ligands influence the risk of KSHV infection.

Methods

A case-control study was performed in Xinjiang, a KSHV-endemic region of China. We recruited 299 individuals with HIV, including 123 KSHV-seropositive persons and 176 KSHV-seronegative controls. We used logistic regression and the MiDAS package to evaluate the association between KIR/HLA-I polymorphisms and KSHV infection.

Results

HLA-A*31:01, HLA-C*03:04, and HLA-C*12:03 were found to be associated with KSHV infection, with A*31:01 showing a protective effect under 3 different models (dominant: 0.30 [95% confidence interval {CI}, .08-.82], P = .031; additive: 0.30 [95% CI, .09-.80], P = .030; overdominant: 0.31 [95% CI, .09-.88], P = .042). The effect of A*31:01 might cause the variants of amino acid at HLA-A position 56, with individuals carrying an arginine having a lower KSHV infection risk. The increased homozygous KIR2DL3 was associated with a relatively high KSHV viral load (16.30% vs 41.94%, P = .010).

Conclusions

This study provides further insight into the link between HLA-I alleles and KIR genes and KSHV infection, highlighting KSHV-susceptible variants of HLA-I and KSHV replication caused by specific KIR genotype, and revealing a potential role of KIR-mediated natural killer cell activation in anti-KSHV infection.

Mapping the interplay between NK cells and HIV: therapeutic implications

Although highly effective at durably suppressing plasma HIV-1 viremia, combination antiretroviral therapy (ART) treatment regimens do not eradicate the virus, which persists in long-lived CD4+ T cells. This latent viral reservoir serves as a source of plasma viral rebound following treatment interruption, thus requiring lifelong adherence to ART. Additionally, challenges remain related not only to access to therapy but also to a higher prevalence of comorbidities with an inflammatory etiology in treated HIV-1+ individuals, underscoring the need to explore therapeutic alternatives that achieve sustained virologic remission in the absence of ART. Natural killer (NK) cells are uniquely positioned to positively impact antiviral immunity, in part due to the pleiotropic nature of their effector functions, including the acquisition of memory-like features, and, therefore, hold great promise for transforming HIV-1 therapeutic modalities. In addition to defining the ability of NK cells to contribute to HIV-1 control, this review provides a basic immunologic understanding of the impact of HIV-1 infection and ART on the phenotypic and functional character of NK cells. We further delineate the qualities of "memory" NK cell populations, as well as the impact of HCMV on their induction and subsequent expansion in HIV-1 infection. We conclude by highlighting promising avenues for optimizing NK cell responses to improve HIV-1 control and effect a functional cure, including blockade of inhibitory NK receptors, TLR agonists to promote latency reversal and NK cell activation, CAR NK cells, BiKEs/TriKEs, and the role of HIV-1-specific bNAbs in NK cell-mediated ADCC activity against HIV-1-infected cells.

Association of iKIR-mismatch model and donor aKIRs with better outcome in haploidentical hematopoietic stem cell transplantation for acute myeloid leukemia

Objectives

Killer cell immunoglobulin like receptor (KIR) can trigger the alloreactivity of NK cells. However, there is no clear consensus as to their function. Here, we investigated the potential influence of KIR mismatch and KIR alleles on the outcome of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) in acute myeloid leukemia (AML) patients.

Method

Data from 79 AML patients treated with haplo-HSCT were retrospectively analyzed. HLA-C genotyping was determined by the PCR-rSSO method. KIR, HLA-A and HLA-B genotyping was performed by the PCR-SSP method. Cox proportional hazards model and Kaplan-Meier survival curves were used for analysis.

Results

Both KIR ligand mismatch (KLM) group and KIR receptor-ligand mismatch (RLM) group were associated with a decreased risk in aGVHD and relapse rate (RR), and better overall survival (OS) compared to the KIR ligand matching and receptor-ligand matching groups, respectively (aGVHD: KLM: p=0.047, HR:0.235; RLM: p<0.001, HR:0.129; RR: KLM: p=0.049, HR:0.686, RLM: p=0.017, HR:0.200;OS:KLM: p=0.012, HR: 0.298, RLM: p=0.021, HR:0.301). RLM was more accurate at predicting relapse and aGVHD compared with KLM (aGVHD: p=0.009; RR: p=0.039). Patients with greater number of donor activating KIRs (aKIR) had a lower incidence of aGVHD and relapse, and the benefits correlated with the increase in the number of donor aKIRs (aGVHD: p=0.019, HR:0.156; RR: p=0.037, HR:0.211). Patients with RLM and the highest number of donor aKIRs had the lowest RR, lowest incidence of aGVHD and best OS.

Conclusions

Both KLM and RLM reduced the risk of aGVHD and relapse after haplo-HSCT in AML patients, and RLM showed superiority in predicting HSCT outcome. The synergistic effects of RLM and donor aKIRs can provide a better donor selection strategy to improve haplo-HSCT outcome in AML patients.

Evaluation of the Anticoccidial Activity of Sheep Bile against Eimeria stiedae Oocysts and Sporozoites of Rabbits: An In Vitro Study

Coccidiosis is one of the most common infectious diseases that causes digestive problems in rabbits, leading to global economic losses. This study was conducted to evaluate the effects of bile obtained from sheep gallbladder on the sporulation and morphology of Eimeria stiedae oocysts and sporozoites affecting rabbit liver cells and to determine the best concentration for sporulation inhibition. Sporulation inhibition per milliliter was measured in samples exposed to five concentrations of sheep bile (SB) in a 2.5% potassium dichromate solution: 12.5%, 25%, 50%, 75%, and 100% concentrations for oocysticidal activity and 125, 250, 500, 750, and 1000 μg/mL concentrations for antisporozoidal activity. A bioassay was performed to assess the in vitro anticoccidial activity of sheep bile against E. stiedae oocysts and sporozoite sporulation. In this assay, six-well plates with 5 mL of bile containing 1000 oocysts showed unsporulated oocysticidal activity after 48, 72, and 96 h and antisporozoidal activity after 12 and 24 h. A chemical assay was performed via infrared spectroscopy to investigate the presence of several anticipated active chemical compounds in sheep bile. Sheep bile was able to inhibit E. stiedae oocysts at 100% and 75% concentrations by about 91% and 81%, respectively. In addition, SB had the highest inhibition of E. stiedae sporozoite viability (92%) at a concentration of 1000 μg/mL and had the lowest inhibition of 8% at a concentration of 125 μg/mL. An increase in the incubation time and a higher dose generally increased the inhibition rate. The results showed that sheep gallbladder bile is effective due to its inhibitory potential and effect on the coccidian oocyst sporulation of E. stiedae. Further studies are needed to determine the precise active chemicals present in SB and their modes of action and application in vivo.

KIR-HLA gene diversities and susceptibility to lung cancer

Killer-cell immunoglobulin-like receptors (KIR) are essential for acquiring natural killer (NK) cell effector function, which is modulated by a balance between the net input of signals derived from inhibitory and activating receptors through engagement by human leukocyte antigen (HLA) class I ligands. KIR and HLA loci are polygenic and polymorphic and exhibit substantial variation between individuals and populations. We attempted to investigate the contribution of KIR complex and HLA class I ligands to the genetic predisposition to lung cancer in the native population of southern Iran. We genotyped 16 KIR genes for a total of 232 patients with lung cancer and 448 healthy controls (HC), among which 85 patients and 178 HCs were taken into account for evaluating combined KIR-HLA associations. KIR2DL2 and 2DS2 were increased significantly in patients than in controls, individually (OR 1.63, and OR 1.42, respectively) and in combination with HLA-C1 ligands (OR 1.99, and OR 1.93, respectively). KIR3DS1 (OR 0.67) and 2DS1 (OR 0.69) were more likely presented in controls in the absence of their relative ligands. The incidence of CxTx subset was increased in lung cancer patients (OR 1.83), and disease risk strikingly increased by more than fivefold among genotype ID19 carriers (a CxTx genotype that carries 2DL2 in the absence of 2DS2, OR 5.92). We found that genotypes with iKIRs > aKIRs (OR 1.67) were more frequently presented in lung cancer patients. Additionally, patients with lung cancer were more likely to carry the combination of CxTx/2DS2 compared to controls (OR 2.04), and iKIRs > aKIRs genotypes in the presence of 2DL2 (OR 2.05) increased the likelihood of lung cancer development. Here we report new susceptibility factors and the contribution of KIR and HLA-I encoding genes to lung cancer risk, highlighting an array of genetic effects and disease setting which regulates NK cell responsiveness. Our results suggest that inherited KIR genes and HLA-I ligands specifying the educational state of NK cells can modify lung cancer risk.

Host KIR/HLA-C Genotypes Determine HIV-Mediated Changes of the NK Cell Repertoire and Are Associated With Vpu Sequence Variations Impacting Downmodulation of HLA-C

NK cells play a pivotal role in viral immunity, utilizing a large array of activating and inhibitory receptors to identify and eliminate virus-infected cells. Killer-cell immunoglobulin-like receptors (KIRs) represent a highly polymorphic receptor family, regulating NK cell activity and determining the ability to recognize target cells. Human leukocyte antigen (HLA) class I molecules serve as the primary ligand for KIRs. Herein, HLA-C stands out as being the dominant ligand for the majority of KIRs. Accumulating evidence indicated that interactions between HLA-C and its inhibitory KIR2DL receptors (KIR2DL1/L2/L3) can drive HIV-1-mediated immune evasion and thus may contribute to the intrinsic control of HIV-1 infection. Of particular interest in this context is the recent observation that HIV-1 is able to adapt to host HLA-C genotypes through Vpu-mediated downmodulation of HLA-C. However, our understanding of the complex interplay between KIR/HLA immunogenetics, NK cell-mediated immune pressure and HIV-1 immune escape is still limited. Therefore, we investigated the impact of specific KIR/HLA-C combinations on the NK cell receptor repertoire and HIV-1 Vpu protein sequence variations of 122 viremic, untreated HIV-1⁺ individuals. Compared to 60 HIV-1^- controls, HIV-1 infection was associated with significant changes within the NK cell receptor repertoire, including reduced percentages of NK cells expressing NKG2A, CD8, and KIR2DS4. In contrast, the NKG2C⁺ and KIR3DL2⁺ NK cell sub-populations from HIV-1⁺ individuals was enlarged compared to HIV-1^- controls. Stratification along KIR/HLA-C genotypes revealed a genotype-dependent expansion of KIR2DL1⁺ NK cells that was ultimately associated with increased binding affinities between KIR2DL1 and HLA-C allotypes. Lastly, our data hinted to a preferential selection of Vpu sequence variants that were associated with HLA-C downmodulation in individuals with high KIR2DL/HLA-C binding affinities. Altogether, our study provides evidence that HIV-1-associated changes in the KIR repertoire of NK cells are to some extent predetermined by host KIR2DL/HLA-C genotypes. Furthermore, analysis of Vpu sequence polymorphisms indicates that differential KIR2DL/HLA-C binding affinities may serve as an additional mechanism how host genetics impact immune evasion by HIV-1.

Immunogenomics of Killer Cell Immunoglobulin-Like Receptor (KIR) and HLA Class I: Coevolution and Consequences for Human Health

Interactions of killer cell immunoglobin-like receptors (KIR) with human leukocyte antigens (HLA) class I regulate effector functions of key cytotoxic cells of innate and adaptive immunity. The extreme diversity of this interaction is genetically determined, having evolved in the ever-changing environment of pathogen exposure. Diversity of KIR and HLA genes is further facilitated by their independent segregation on separate chromosomes. That fetal implantation relies on many of the same types of immune cells as infection control places certain constraints on the evolution of KIR interactions with HLA. Consequently, specific inherited combinations of receptors and ligands may predispose to specific immune-mediated diseases, including autoimmunity. Combinatorial diversity of KIR and HLA class I can also differentiate success rates of immunotherapy directed to these diseases. Progress toward both etiopathology and predicting response to therapy is being achieved through detailed characterization of the extent and consequences of the combinatorial diversity of KIR and HLA. Achieving these goals is more tractable with the development of integrated analyses of molecular evolution, function, and pathology that will establish guidelines for understanding and managing risks. Here, we present what is known about the coevolution of KIR with HLA class I and the impact of their complexity on immune function and homeostasis.

NK Cells in Protection from HIV Infection

Some people, known as HIV-exposed seronegative (HESN) individuals, remain uninfected despite high levels of exposure to HIV. Understanding the mechanisms underlying their apparent resistance to HIV infection may inform strategies designed to protect against HIV infection. Natural Killer (NK) cells are innate immune cells whose activation state depends on the integration of activating and inhibitory signals arising from cell surface receptors interacting with their ligands on neighboring cells. Inhibitory NK cell receptors use a subset of major histocompatibility (MHC) class I antigens as ligands. This interaction educates NK cells, priming them to respond to cells with reduced MHC class I antigen expression levels as occurs on HIV-infected cells. NK cells can interact with both autologous HIV-infected cells and allogeneic cells bearing MHC antigens seen as non self by educated NK cells. NK cells are rapidly activated upon interacting with HIV-infected or allogenic cells to elicit anti-viral activity that blocks HIV spread to new target cells, suppresses HIV replication, and kills HIV-infected cells before HIV reservoirs can be seeded and infection can be established. In this manuscript, we will review the epidemiological and functional evidence for a role for NK cells in protection from HIV infection.

Natural Killer Cells in Antibody Independent and Antibody Dependent HIV Control

Infection with the human immunodeficiency virus (HIV), when left untreated, typically leads to disease progression towards acquired immunodeficiency syndrome. Some people living with HIV (PLWH) control their virus to levels below the limit of detection of standard viral load assays, without treatment. As such, they represent examples of a functional HIV cure. These individuals, called Elite Controllers (ECs), are rare, making up <1% of PLWH. Genome wide association studies mapped genes in the major histocompatibility complex (MHC) class I region as important in HIV control. ECs have potent virus specific CD8⁺ T cell responses often restricted by protective MHC class I antigens. Natural Killer (NK) cells are innate immune cells whose activation state depends on the integration of activating and inhibitory signals arising from cell surface receptors interacting with their ligands on neighboring cells. Inhibitory NK cell receptors also use a subset of MHC class I antigens as ligands. This interaction educates NK cells, priming them to respond to HIV infected cell with reduced MHC class I antigen expression levels. NK cells can also be activated through the crosslinking of the activating NK cell receptor, CD16, which binds the fragment crystallizable portion of immunoglobulin G. This mode of activation confers NK cells with specificity to HIV infected cells when the antigen binding portion of CD16 bound immunoglobulin G recognizes HIV Envelope on infected cells. Here, we review the role of NK cells in antibody independent and antibody dependent HIV control.

A Protective HLA Extended Haplotype Outweighs the Major COVID-19 Risk Factor Inherited From Neanderthals in the Sardinian Population

Sardinia has one of the lowest incidences of hospitalization and related mortality in Europe and yet a very high frequency of the Neanderthal risk locus variant on chromosome 3 (rs35044562), considered to be a major risk factor for a severe SARS-CoV-2 disease course. We evaluated 358 SARS-CoV-2 patients and 314 healthy Sardinian controls. One hundred and twenty patients were asymptomatic, 90 were pauci-symptomatic, 108 presented a moderate disease course and 40 were severely ill. All patients were analyzed for the Neanderthal-derived genetic variants reported as being protective (rs1156361) or causative (rs35044562) for severe illness. The β°39 C>T Thalassemia variant (rs11549407), HLA haplotypes, KIR genes, KIRs and their HLA class I ligand combinations were also investigated. Our findings revealed an increased risk for severe disease in Sardinian patients carrying the rs35044562 high risk variant [OR 5.32 (95% CI 2.53 - 12.01), p = 0.000]. Conversely, the protective effect of the HLA-A*02:01, B*18:01, DRB*03:01 three-loci extended haplotype in the Sardinian population was shown to efficiently contrast the high risk of a severe and devastating outcome of the infection predicted for carriers of the Neanderthal locus [OR 15.47 (95% CI 5.8 - 41.0), p < 0.0001]. This result suggests that the balance between risk and protective immunogenetic factors plays an important role in the evolution of COVID-19. A better understanding of these mechanisms may well turn out to be the biggest advantage in the race for the development of more efficient drugs and vaccines.

Donor with HLA-C2 is associated with acute rejection following liver transplantation in southern Chinese

Apart from presenting peptides to T cells, class I HLA molecules serve as ligands for KIRs and regulate the response of NK cells. The role played by HLA and KIR in the acute rejection (AR) following liver transplantation has been controversial. In this retrospective study, we assessed the influence of class I HLA alleles, HLA matching between donor-recipient pairs, recipient KIR and donor HLA ligands on AR following liver transplantation in southern Chinese. 143 recipients and 78 donors obtained from a single transplant center were included in the study cohort. 33 recipients with histologically confirmed AR were observed. We found that the incidence of AR did not correlate with donor or recipient class I HLA alleles and HLA matching. Neither recipient KIR gene nor the KIR genotype was associated with AR, moreover, high-resolution genotyping of 14 functional KIR genes of recipients showed that no KIR allele was independently associated with AR. However, the frequency of HLA-C2⁺ donor significantly increased in AR group compared with NAR group (52.9% vs. 24.6%, P = 0.03). In the presence of HLA-C2 by the donor allograft, AR was more frequently observed in recipients with normal expressed KIR2DS4 (43.8% vs. 15.0%, P = 0.03). Donor with HLA-C2 is therefore a major determinant of AR, which can confer risk effect in liver transplantation. Our findings can provide valuable clues for better understanding pathogenesis of AR and have important clinical implications in liver transplantation for Chinese. This article is protected by copyright. All rights reserved.

A NK Cell Odyssey: From Bench to Therapeutics Against Hematological Malignancies

In 1975 two independent groups noticed the presence of immune cells with a unique ability to recognize and eliminate transformed hematopoietic cells without any prior sensitization or expansion of specific clones. Since then, NK cells have been the axis of thousands of studies that have resulted until June 2021, in more than 70 000 publications indexed in PubMed. As result of this work, which include approaches in vitro, in vivo, and in natura, it has been possible to appreciate the role played by the NK cells, not only as effectors against specific pathogens, but also as regulators of the immune response. Recent advances have revealed previous unidentified attributes of NK cells including the ability to adapt to new conditions under the context of chronic infections, or their ability to develop some memory-like characteristics. In this review, we will discuss significant findings that have rule our understanding of the NK cell biology, the developing of these findings into new concepts in immunology, and how these conceptual platforms are being used in the design of strategies for cancer immunotherapy.

Individualized Constellation of Killer Cell Immunoglobulin-Like Receptors and Cognate HLA Class I Ligands that Controls Natural Killer Cell Antiviral Immunity Predisposes COVID-19

Background: The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection causes coronavirus disease-2019 (COVID-19) in some individuals, while the majority remain asymptomatic. Natural killer (NK) cells play an essential role in antiviral defense. NK cell maturation and function are regulated mainly by highly polymorphic killer cell immunoglobulin-like receptors (KIR) and cognate HLA class I ligands. Herein, we tested our hypothesis that the individualized KIR and HLA class I ligand combinations that control NK cell function determine the outcome of SARS-CoV-2 infection.

Methods: We characterized KIR and HLA genes in 200 patients hospitalized for COVID-19 and 195 healthy general population controls.

Results: The KIR3DL1⁺HLA-Bw4⁺ [Odds ratio (OR) = 0.65, p = 0.03] and KIR3DL2⁺HLA-A3/11⁺ (OR = 0.6, p = 0.02) combinations were encountered at significantly lower frequency in COVID-19 patients than in the controls. Notably, 40% of the patients lacked both of these KIR⁺HLA⁺ combinations compared to 24.6% of the controls (OR = 2.04, p = 0.001). Additionally, activating receptors KIR2DS1⁺KIR2DS5⁺ are more frequent in patients with severe COVID-19 than patients with mild disease (OR = 1.8, p = 0.05). Individuals carrying KIR2DS1⁺KIR2DS5⁺ genes but missing either KIR3DL1⁺HLA-Bw4⁺ combination (OR = 1.73, p = 0.04) or KIR3DL2⁺HLA-A3/11⁺ combination (OR = 1.75, p = 0.02) or both KIR3DL1⁺HLA-Bw4⁺ and KIR2DL2⁺HLA-A3/11⁺ combinations (OR = 1.63, p = 0.03) were more frequent in the COVID-19 cohort compared to controls.

Conclusions: The absence of KIR3DL1⁺HLA-Bw4⁺ and KIR3DL2⁺HLA-A3/11⁺ combinations presumably yields inadequate NK cell maturation and reduces anti-SARS-CoV-2 defense, causing COVID-19. An increased frequency of KIR2DS1⁺KIR2DS5⁺ in severe COVID-19 patients suggests vigorous NK cell response triggered via these activating receptors and subsequent production of exuberant inflammatory cytokines responsible for severe COVID-19. Our results demonstrate that specific KIR-HLA combinations that control NK cell maturation and function are underlying immunogenetic variables that determine the dual role of NK cells in mediating beneficial antiviral and detrimental pathologic action. These findings offer a framework for developing potential host genetic biomarkers to distinguish individuals prone to COVID-19.

Practical Considerations and Workflow in Utilizing KIR Genotyping in Transplantation Medicine

This chapter is intended to serve as a practical guide for establishing a workflow using sequence-specific polymorphism PCR (SSP-PCR) for killer cell immunoglobulin-like receptor (KIR) genotyping in a clinical setting, especially in allogeneic hematopoietic stem cell transplantation (HSCT). As clinical evidence accumulates on the application of KIR and HLA genetics to guide donor selection in HSCT, there is an increasing need for KIR genotyping in clinical settings, and thus medical institutes may need to build this capability. Among the various KIR genotyping approaches now available, SSP-PCR methods are well-established and are the most cost-effective and will likely be the method of choice especially when expenses will be passed on to the patient. The protocol described in this chapter developed by Vilches et al. features small amplicon PCR and is suitable for KIR genotyping using FFPE-derived DNA as well as DNA extracted from blood samples. Setting up a laboratory workflow for in-house KIR genotyping is relatively straightforward; in this chapter, considerations for KIR genotyping to guide clinical decisions are discussed.In HSCT, a main objective of KIR genotyping is to apply the genetic analysis to predict donor and recipient combinations that have the most potential to produce NK cell alloresponses either through the missing-self mechanism or by action associated with activating KIR. The desired effects are reduction in acute GVHD and relapse rates and enhancement of overall survival. The information herein may also be useful to clinical laboratories considering the application of KIR genotyping in areas such as solid organ transplantation, NK cell-based treatment in other forms of cancer and autoimmune diseases, humanized antibody treatment, regenerative medicine, and reproductive medicine. Some background knowledge on KIR genetics will be necessary in managing a KIR genotyping platform. This chapter aims to address the main difficulties often encountered by physicians in understanding the KIR system, such as basic aspects of the nomenclature of KIR genes and haplotypes, genotypes, and determining presence/absence of KIR ligands in the patient and donor from the extensively diversified HLA class I allotypes. In describing the workflow, emphasis has been placed on the processes after genotype PCR and gel image acquisition: haplotype inference, generating B content scores, deduction of KIR ligands from HLA typing results, and the emerging algorithms for donor selection based on KIR and HLA genetics.

Remarkably low KIR and HLA diversity in Amerindians reveals signatures of strong purifying selection shaping the centromeric KIR region

The killer-cell immunoglobulin-like receptors (KIR) recognize human leukocyte antigen (HLA) molecules to regulate the cytotoxic and inflammatory responses of natural killer cells. KIR genes are encoded by a rapidly evolving gene family on chromosome 19 and present an unusual variation of presence and absence of genes and high allelic diversity. Although many studies have associated KIR polymorphism with susceptibility to several diseases over the last decades, the high-resolution allele-level haplotypes have only recently started to be described in populations. Here, we use a highly innovative custom next-generation sequencing method that provides a state-of-art characterization of KIR and HLA diversity in 706 individuals from eight unique South American populations: five Amerindian populations from Brazil (three Guarani and two Kaingang); one Amerindian population from Paraguay (Aché); and two urban populations from Southern Brazil (European and Japanese descendants from Curitiba). For the first time, we describe complete high-resolution KIR haplotypes in South American populations, exploring copy number, linkage disequilibrium, and KIR-HLA interactions. We show that all Amerindians analyzed to date exhibit the lowest numbers of KIR-HLA interactions among all described worldwide populations, and that 83-97% of their KIR-HLA interactions rely on a few HLA-C molecules. Using multiple approaches, we found signatures of strong purifying selection on the KIR centromeric region, which codes for the strongest NK cell educator receptors, possibly driven by the limited HLA diversity in these populations. Our study expands the current knowledge of KIR genetic diversity in populations to understand KIR-HLA coevolution and its impact on human health and survival.

Natural killer-cell immunoglobulin-like receptors trigger differences in immune response to SARS-CoV-2 infection

Background

The diversity in the clinical course of COVID-19 has been related to differences in innate and adaptative immune response mechanisms. Natural killer (NK) lymphocytes are critical protagonists of human host defense against viral infections. It would seem that reduced circulating levels of these cells have an impact on COVID-19 progression and severity. Their activity is strongly regulated by killer-cell immuno-globulin-like receptors (KIRs) expressed on the NK cell surface. The present study’s focus was to investigate the impact of KIRs and their HLA Class I ligands on SARS-CoV-2 infection.

Methods

KIR gene frequencies, KIR haplotypes, KIR ligands and combinations of KIRs and their HLA Class I ligands were investigated in 396 Sardinian patients with SARS-CoV-2 infection. Comparisons were made between 2 groups of patients divided according to disease severity: 240 patients were symptomatic or paucisymptomatic (Group A), 156 hospitalized patients had severe disease (Group S). The immunogenetic characteristics of patients were also compared to a population group of 400 individuals from the same geographical areas.

Results

Substantial differences were obtained for KIR genes, KIR haplotypes and KIR-HLA ligand combinations when comparing patients of Group S to those of Group A. Patients in Group S had a statistically significant higher frequency of the KIR A/A haplotype compared to patients in Group A [34.6% vs 23.8%, OR = 1.7 (95% CI 1.1–2.6); P = 0.02, Pc = 0.04]. Moreover, the KIR2DS2/HLA C1 combination was poorly represented in the group of patients with severe symptoms compared to those of the asymptomatic-paucisymptomatic group [33.3% vs 50.0%, OR = 0.5 (95% CI 0.3–0.8), P = 0.001, Pc = 0.002]. Multivariate analysis confirmed that, regardless of the sex and age of the patients, the latter genetic variable correlated with a less severe disease course [OR_M = 0.4 (95% CI 0.3–0.7), P_M = 0.0005, P_MC = 0.005].

Conclusions

The KIR2DS2/HLA C1 functional unit resulted to have a strong protective effect against the adverse outcomes of COVID-19. Combined to other well known factors such as advanced age, male sex and concomitant autoimmune diseases, this marker could prove to be highly informative of the disease course and thus enable the timely intervention needed to reduce the mortality associated with the severe forms of SARS-CoV-2 infection. However, larger studies in other populations as well as experimental functional studies will be needed to confirm our findings and further pursue the effect of KIR receptors on NK cell immune-mediated response to SARS-Cov-2 infection.

Following Transplantation for Acute Myelogenous Leukemia, Donor KIR Cen B02 Better Protects against Relapse than KIR Cen B01

In the treatment of acute myelogenous leukemia with allogeneic hematopoietic cell transplantation, we previously demonstrated that there is a greater protection from relapse of leukemia when the hematopoietic cell transplantation donor has either the Cen B/B KIR genotype or a genotype having two or more KIR B gene segments. In those earlier analyses, KIR genotyping could only be assessed at the low resolution of gene presence or absence. To give the analysis greater depth, we developed high-resolution KIR sequence-based typing that defines all the KIR alleles and distinguishes the expressed alleles from those that are not expressed. We now describe and analyze high-resolution KIR genotypes for 890 donors of this human transplant cohort. Cen B01 and Cen B02 are the common CenB haplotypes, with Cen B02 having evolved from Cen B01 by deletion of the KIR2DL5, 2DS3/5, 2DP1, and 2DL1 genes. We observed a consistent trend for Cen B02 to provide stronger protection against relapse than Cen B01 This correlation indicates that protection depends on the donor having inhibitory KIR2DL2 and/or activating KIR2DS2, and is enhanced by the donor lacking inhibitory KIR2DL1, 2DL3, and 3DL1. High-resolution KIR typing has allowed us to compare the strength of the interactions between the recipient's HLA class I and the KIR expressed by the donor-derived NK cells and T cells, but no clinically significant interactions were observed. The trend observed between donor Cen B02 and reduced relapse of leukemia points to the value of studying ever larger transplant cohorts.

HLAs, TCRs, and KIRs, a Triumvirate of Human Cell-Mediated Immunity

In all human cells, human leukocyte antigen (HLA) class I glycoproteins assemble with a peptide and take it to the cell surface for surveillance by lymphocytes. These include natural killer (NK) cells and γδ T cells of innate immunity and αβ T cells of adaptive immunity. In healthy cells, the presented peptides derive from human proteins, to which lymphocytes are tolerant. In pathogen-infected cells, HLA class I expression is perturbed. Reduced HLA class I expression is detected by KIR and CD94:NKG2A receptors of NK cells. Almost any change in peptide presentation can be detected by αβ CD8⁺ T cells. In responding to extracellular pathogens, HLA class II glycoproteins, expressed by specialized antigen-presenting cells, present peptides to αβ CD4⁺ T cells. In comparison to the families of major histocompatibility complex (MHC) class I, MHC class II and αβ T cell receptors, the antigenic specificity of the γδ T cell receptors is incompletely understood.

Analysis of genomic DNA from medieval plague victims suggests long-term effect of Yersinia pestis on human immunity genes

Pathogens and associated outbreaks of infectious disease exert selective pressure on human populations, and any changes in allele frequencies that result may be especially evident for genes involved in immunity. In this regard, the 1346-1353 Yersinia pestis-caused Black Death pandemic, with continued plague outbreaks spanning several hundred years, is one of the most devastating recorded in human history. To investigate the potential impact of Y. pestis on human immunity genes we extracted DNA from 36 plague victims buried in a mass grave in Ellwangen, Germany in the 16th century. We targeted 488 immune-related genes, including HLA, using a novel in-solution hybridization capture approach. In comparison with 50 modern native inhabitants of Ellwangen, we find differences in allele frequencies for variants of the innate immunity proteins Ficolin-2 and NLRP14 at sites involved in determining specificity. We also observed that HLA-DRB1*13 is more than twice as frequent in the modern population, whereas HLA-B alleles encoding an isoleucine at position 80 (I-80+), HLA C*06:02 and HLA-DPB1 alleles encoding histidine at position 9 are half as frequent in the modern population. Simulations show that natural selection has likely driven these allele frequency changes. Thus, our data suggests that allele frequencies of HLA genes involved in innate and adaptive immunity responsible for extracellular and intracellular responses to pathogenic bacteria, such as Y. pestis, could have been affected by the historical epidemics that occurred in Europe.

HLA-A alleles influencing NK cell function impact AML relapse following allogeneic hematopoietic cell transplantation

HLA-B allotypes exhibiting the Bw4 epitope trigger variable inhibitory signaling of KIR3DL1 receptor types, where strong inhibitory HLA-B and KIR3DL1 allele combinations are associated with increased risk for relapse of acute myelogenous leukemia (AML) following allogeneic hematopoietic cell transplantation (HCT). Several HLA-A allotypes also exhibit the Bw4 epitope. Studies with natural killer (NK) cell clones have demonstrated NK inhibition via KIR3DL1 by HLA-A Bw4+ allotypes, but did not delineate strengths of inhibition or hierarchies of NK education. Using primary NK cells from healthy donors, we demonstrate that HLA-A*23, HLA-A*24, and HLA-A*32 proteins are expressed at different densities and exhibit different capacities to educate and inhibit KIR3DL1-expressing NK cells in vitro. Among the HLA-A Bw4+ allotypes, HLA-A*24 and HLA-A*32 demonstrate the strongest inhibitory capacity. To determine if HLA-A allotypes with strong inhibitory capacity have similar negative impact in allogeneic HCT as HLA-B Bw4+ allotypes, we performed a retrospective analysis of 1729 patients with AML who received an allogeneic HCT from a 9/10 or 10/10 HLA allele-matched unrelated donor. Examination of the donor-recipient pairs whose Bw4 epitope was exclusively contributed from HLA-A*24 and A*32 allotypes revealed that patients with HLA-A*24 who received an allograft from a KIR3DL1+ donor experienced a higher risk of disease relapse (hazard ratio, 1.65; 95% confidence interval, 1.17-2.32; P = .004) when compared with patients without a Bw4 epitope. These findings indicate that despite weak affinity interactions with KIR3DL1, common HLA-A allotypes with the Bw4 epitope can interact with KIR3DL1+ donor NK cells with clinically meaningful impact and provide additional insight to donor NK alloreactivity in HLA-matched HCT.

Uterine natural killer cells and recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA), termed as two or more consecutive pregnancy loss is a great problem for some women of childbearing age. A large number of evidence confirm that there may be an immune background of RSA. As a member of the innate immune system, uterine natural killer (uNK) cells account for about 70% of total lymphocytes during pregnancy and play a critical role in the establishment and maintenance of pregnancy. This review mainly introduces the phenotype, origin, receptor, and function of uNK cells to illuminate its relationship with RSA.

The combinatorial diversity of KIR and HLA class I allotypes in Peninsular Malaysia

Killer cell immunoglobulin-like receptors (KIRs) interact with polymorphic human leucocyte antigen (HLA) class I molecules, modulating natural killer (NK) cell functions and affecting both the susceptibility and outcome of immune-mediated diseases. The KIR locus is highly diverse in gene content, copy number and allelic polymorphism within individuals and across geographical populations. To analyse currently under-represented Asian and Pacific populations, we investigated the combinatorial diversity of KIR and HLA class I in 92 unrelated Malay and 75 Malaysian Chinese individuals from the Malay Peninsula. We identified substantial allelic and structural diversity of the KIR locus in both populations and characterized novel variations at each analysis level. The Malay population is more diverse than Malay Chinese, likely representing a unique history including admixture with immigrating populations spanning several thousand years. Characterizing the Malay population are KIR haplotypes with large structural variants present in 10% individuals, and KIR and HLA alleles previously identified in Austronesian populations. Despite the differences in ancestries, the proportion of HLA allotypes that serve as KIR ligands is similar in each population. The exception is a significantly reduced frequency of interactions of KIR2DL1 with C2+ HLA-C in the Malaysian Chinese group, caused by the low frequency of C2+ HLA. One likely implication is a greater protection from preeclampsia, a pregnancy disorder associated with KIR2DL1, which shows higher incidence in the Malay than in the Malaysian Chinese. This first complete, high-resolution, characterization of combinatorial diversity of KIR and HLA in Malaysians will form a valuable reference for future clinical and population studies.

The Role of the HLA Class I α2 Helix in Determining Ligand Hierarchy for the Killer Cell Ig-like Receptor 3DL1

HLA class I molecules that represent ligands for the inhibitory killer cell Ig-like receptor (KIR) 3DL1 found on NK cells are categorically defined as those HLA-A and HLA-B allotypes containing the Bw4 motif, yet KIR3DL1 demonstrates hierarchical recognition of these HLA-Bw4 ligands. To better understand the molecular basis underpinning differential KIR3DL1 recognition, the HLA-A^Bw4 family of allotypes were investigated. Transfected human 721.221 cells expressing HLA-A*32:01 strongly inhibited primary human KIR3DL1⁺ NK cells, whereas HLA-A*24:02 and HLA-A*23:01 displayed intermediate potency and HLA-A*25:01 failed to inhibit activation of KIR3DL1⁺ NK cells. Structural studies demonstrated that recognition of HLA-A*24:02 by KIR3DL1 used identical contacts as the potent HLA-B*57:01 ligand. Namely, the D1-D2 domains of KIR3DL1 were placed over the α1 helix and α2 helix of the HLA-A*24:02 binding cleft, respectively, whereas the D0 domain contacted the side of the HLA-A*24:02 molecule. Nevertheless, functional analyses showed KIR3DL1 recognition of HLA-A*24:02 was more sensitive to substitutions within the α2 helix of HLA-A*24:02, including residues Ile¹⁴² and Lys¹⁴⁴ Furthermore, the presence of Thr¹⁴⁹ in the α2 helix of HLA-A*25:01 abrogated KIR3DL1⁺ NK inhibition. Together, these data demonstrate a role for the HLA class I α2 helix in determining the hierarchy of KIR3DL1 ligands. Thus, recognition of HLA class I is dependent on a complex interplay between the peptide repertoire, polymorphisms within and proximal to the Bw4 motif, and the α2 helix. Collectively, the data furthers our understanding of KIR3DL1 ligands and will inform genetic association and immunogenetics studies examining the role of KIR3DL1 in disease settings.

A comprehensive overview on the genetics of Behçet's disease

Behçet's disease (BD) is a systemic and inflammatory disease, characterized mainly by recurrent oral and genital ulcers, eye involvement, and skin lesions. Although the exact etiopathogenesis of BD remains unrevealed, a bulk of studies have implicated the genetic contributing factors as critical players in disease predisposition. In countries along the Silk Road, human leukocyte antigen (HLA)-B51 has been reported as the strongest genetically associated factor for BD. Genome-wide association studies, local genetic polymorphism studies, and meta-analysis of combined data from Turkish, Iranian, and Japanese populations have also identified new genetic associations with BD. Among these, other HLA alleles such as HLA-B*15, HLA-B*27, HLA-B*57, and HLA-A*26 have been found as independent risk factors for BD, whereas HLA-B*49 and HLA-A*03 are independent protective alleles for BD. Moreover, other genes have also reached the genome-wide significance level of association with BD susceptibility, including IL10, IL23R-IL12RB2, IL12A, CCR1-CCR3, STAT4, TNFAIP3, ERAP1, KLRC4, and FUT2. Also, several rare nonsynonymous variants in TLR4, IL23R, NOD2, and MEFV genes have been reported to be involved in BD pathogenesis. According to genetic determinants in the loci outside the MHC region that are contributed to the host defense, immunity, and inflammation pathways, it is suggested that immune responses to the pathogen as an important environmental factor and mucosal immunity contribute to BD susceptibility.

Association of Inhibitory Killer Cell Immunoglobulin-like Receptor Ligands With Higher Plasmodium falciparum Parasite Prevalence

Killer cell immunoglobulin-like receptors (KIRs) and their HLA ligands influence the outcome of many infectious diseases. We analyzed the relationship of compound KIR-HLA genotypes with risk of Plasmodium falciparum infection in a longitudinal cohort of 890 Ugandan individuals. We found that presence of HLA-C2 and HLA-Bw4, ligands for inhibitory KIR2DL1 and KIR3DL1, respectively, increased the likelihood of P. falciparum parasitemia in an additive manner. Individuals homozygous for HLA-C2, which mediates strong inhibition via KIR2DL1, had the highest odds of parasitemia, HLA-C1/C2 heterozygotes had intermediate odds, and individuals homozygous for HLA-C1, which mediates weaker inhibition through KIR2DL2/3, had the lowest odds of parasitemia. In addition, higher surface expression of HLA-C, the ligand for inhibitory KIR2DL1/2/3, was associated with a higher likelihood of parasitemia. Together these data indicate that stronger KIR-mediated inhibition confers a higher risk of P. falciparum parasitemia and suggest that KIR-expressing effector cells play a role in mediating antiparasite immunity.

The impact of donor full-length KIR2DS4 in the development of acute and chronic GVHD after unrelated allogeneic HSCT

BACKGROUND

Killer Ig-like receptor 2DS4 (KIR2DS4) is the most prevalent activating killer Ig-like receptor gene. It is divergent and encodes either full-length or deleted allele variants. The studies of donor killer KIR2DS4 in unrelated allogeneic hematopoietic stem cell transplantations were limited.

METHODS

KIR and HLA genotyping were determined in 75 pairs of Chinese pediatric hematologic malignancy patients.

RESULTS

Among the 75 donor-recipient pairs, 77.3% (58/75) of the donors were positive for full-length KIR2DS4 and 22.7% (17/75) were negative. Patients who had donors positive for full-length KIR2DS4 had higher cumulative incidence of aGVHD than patients whose donor negative for full-length KIR2DS4 (86.2% versus 76.5%, P = .038). Multivariate analysis showed full-length KIR2DS4 was the significant factor for I-IV aGVHD (HR = 2.166, 95% CI: 1.01-4.26, P = .025). Subgroup analysis showed that AML and CML patients who received donors negative for full-length KIR2DS4 have a higher cumulative incidences of cGVHD (75% vs 62%, P = .008). There were no significant effects of full-length KIR2DS4 on overall survival (P = .13), relapse-free survival (P = .14), CMV reactivation (P = .52), and relapse (HR = 0.38, 95% CI: 0.09-1.6, P = .1875).

CONCLUSIONS

Our findings indicated a significant correlation of donor full-length KIR2DS4 on aGVHD and cGVHD. These results suggested that combining KIR and HLA genotyping may help make a better sense of transplants in these patients.

Killer Cell Immunoglobulin-like Receptor Variants Are Associated with Protection from Symptoms Associated with More Severe Course in Parkinson Disease

Immune dysfunction plays a role in the development of Parkinson disease (PD). NK cells regulate immune functions and are modulated by killer cell immunoglobulin-like receptors (KIR). KIR are expressed on the surface of NK cells and interact with HLA class I ligands on the surface of all nucleated cells. We investigated KIR-allelic polymorphism to interrogate the role of NK cells in PD. We sequenced KIR genes from 1314 PD patients and 1978 controls using next-generation methods and identified KIR genotypes using custom bioinformatics. We examined associations of KIR with PD susceptibility and disease features, including age at disease onset and clinical symptoms. We identified two KIR3DL1 alleles encoding highly expressed inhibitory receptors associated with protection from PD clinical features in the presence of their cognate ligand: KIR3DL1*015/HLA-Bw4 from rigidity (p _c = 0.02, odds ratio [OR] = 0.39, 95% confidence interval [CI] 0.23-0.69) and KIR3DL1*002/HLA-Bw4i from gait difficulties (p _c = 0.05, OR = 0.62, 95% CI 0.44-0.88), as well as composite symptoms associated with more severe disease. We also developed a KIR3DL1/HLA interaction strength metric and found that weak KIR3DL1/HLA interactions were associated with rigidity (p_c = 0.05, OR = 9.73, 95% CI 2.13-172.5). Highly expressed KIR3DL1 variants protect against more debilitating symptoms of PD, strongly implying a role of NK cells in PD progression and manifestation.

Immunomodulation of the Natural Killer Cell Phenotype and Response during HCV Infection

Hepatitis C virus (HCV) infection develops into chronic hepatitis in over two-thirds of acute infections. While current treatments with direct-acting antivirals (DAAs) achieve HCV eradication in >95% of cases, no vaccine is available and re-infection can readily occur. Natural killer (NK) cells represent a key cellular component of the innate immune system, participating in early defence against infectious diseases, viruses, and cancers. When acute infection becomes chronic, however, NK cell function is altered. This has been well studied in the context of HCV, where changes in frequency and distribution of NK cell populations have been reported. While activating receptors are downregulated on NK cells in both acute and chronic infection, NK cell inhibiting receptors are upregulated in chronic HCV infection, leading to altered NK cell responsiveness. Furthermore, chronic activation of NK cells following HCV infection contributes to liver inflammation and disease progression through enhanced cytotoxicity. Consequently, the NK immune response is a double-edged sword that is a significant component of the innate immune antiviral response, but persistent activation can drive tissue damage during chronic infection. This review will summarise the role of NK cells in HCV infection, and the changes that occur during HCV therapy.

KIR Variation in Iranians Combines High Haplotype and Allotype Diversity With an Abundance of Functional Inhibitory Receptors

Natural killer (NK) cells are innate lymphocytes that eliminate infected and transformed cells. They discriminate healthy from diseased tissue through killer cell Ig-like receptor (KIR) recognition of HLA class I ligands. Directly impacting NK cell function, KIR polymorphism associates with infection control and multiple autoimmune and pregnancy syndromes. Here we analyze KIR diversity of 241 individuals from five groups of Iranians. These five populations represent Baloch, Kurd, and Lur, together comprising 15% of the ethnically diverse Iranian population. We identified 159 KIR alleles, including 11 not previously characterized. We also identified 170 centromeric and 94 telomeric haplotypes, and 15 different KIR haplotypes carrying either a deletion or duplication encompassing one or more complete KIR genes. As expected, comparing our data with those representing major worldwide populations revealed the greatest similarity between Iranians and Europeans. Despite this similarity we observed higher frequencies of KIR3DL1^*001 in Iran than any other population, and the highest frequency of HLA-B^*51, a Bw4-containing allotype that acts as a strong educator of KIR3DL1^*001⁺ NK cells. Compared to Europeans, the Iranians we studied also have a reduced frequency of 3DL1^*004, which encodes an allotype that is not expressed at the NK cell surface. Concurrent with the resulting high frequency of strong viable interactions between inhibitory KIR and polymorphic HLA class I, the majority of KIR-A haplotypes characterized do not express a functional activating receptor. By contrast, the most frequent KIR-B haplotype in Iran expresses only one functional inhibitory KIR and the maximum number of activating KIR. This first complete, high-resolution, characterization of the KIR locus of Iranians will form a valuable reference for future clinical and population studies.

The Education of NK Cells Determines Their Responsiveness to Autologous HIV-Infected CD4 T Cells

Several studies support a role for specific killer immunoglobulin-like receptor (KIR)-HLA combinations in protection from HIV infection and slower progression to AIDS. Natural killer (NK) cells acquire effector functions through education, a process that requires the interaction of inhibitory NK cell receptors with their major histocompatibility complex (MHC) class I (or HLA class I [HLA-I]) ligands. HLA-C allotypes are ligands for the inhibitory KIRs (iKIRs) KIR2DL1, KIR2DL2, and KIR2DL3, whereas the ligand for KIR3DL1 is HLA-Bw4. HIV infection reduces the expression of HLA-A, -B, and -C on the surfaces of infected CD4 (iCD4) T cells. Here we investigated whether education through iKIR-HLA interactions influenced NK cell responses to autologous iCD4 cells. Enriched NK cells were stimulated with autologous iCD4 cells or with uninfected CD4 cells as controls. The capacities of single-positive (sp) KIR2DL1, KIR2DL2, KIR2DL3, and KIR3DL1 NK cells to produce CCL4, gamma interferon (IFN-γ), and/or CD107a were assessed by flow cytometry. Overall, we observed that the potency of NK cell education was directly related to the frequency of each spiKIR⁺ NK cell's ability to respond to the reduction of its cognate HLA ligand on autologous iCD4 cells, as measured by the frequency of production by spiKIR⁺ NK cells of CCL4, IFN-γ, and/or CD107a. Both NK cell education and HIV-mediated changes in HLA expression influenced NK cell responses to iCD4 cells.IMPORTANCE Epidemiological studies show that natural killer (NK) cells have anti-HIV activity: they are able to reduce the risk of HIV infection and/or slow HIV disease progression. How NK cells contribute to these outcomes is not fully characterized. We used primary NK cells and autologous HIV-infected cells to examine the role of education through four inhibitory killer immunoglobulin-like receptors (iKIRs) from persons with HLA types that are able to educate NK cells bearing one of these iKIRs. HIV-infected cells activated NK cells through missing-self mechanisms due to the downmodulation of cell surface HLA expression mediated by HIV Nef and Vpu. A higher frequency of educated than uneducated NK cells expressing each of these iKIRs responded to autologous HIV-infected cells by producing CCL4, IFN-γ, and CD107a. Since NK cells were from non-HIV-infected individuals, they model the consequences of healthy NK cell-HIV-infected cell interactions occurring in the HIV eclipse phase, when new infections are susceptible to extinction.

Family-based Association Study of Killer Cell Immunoglobulin-Like Receptor Genes with Leukemia

NK cell function is controlled by the cell expression of killer immunoglobulin-like receptors (KIRs) and their ligation with the corresponding HLA ligands. Various malignancies have been associated with certain KIRs surface cell expression and various KIR/HLA ligand combinations. Prior research using case/control study design demonstrates the role of KIR and KIR HLA ligands as genetic factor involved in tumor susceptibility. The objective of this study was to investigate the family-based association of KIRs, HLA class I ligands and KIR/ligand combinations with leukemia diagnosis in families having a leukemia diagnosed child. Sixty-seven families that met the index leukemia case criteria (acute lymphoblastic leukemia, ALL, n = 45; acute myeloid leukemia, AML, n = 13; chronic myeloid leukemia, CML, n = 9; first degree healthy relatives n = 159) were examined. Our study consisted of two phases. In Phase1 case-control study, we primarily compared patients to their healthy siblings to asses if a marker or genotype may be associated with leukemia, excluding the impact of the environment. Phase 2 consisted of a secondary family-based association study. KIR genotyping was performed by PCR-SSP method. KIR HLA ligands were defined by direct method using PCR-SSP method and/or indirect base on high resolution typing of HLA-A, -B, -C alleles. Results of phase 1 showed an increase in the frequency of KIR genotype (with a ratio = 0.57; higher frequency for inhibitory KIRs vs. activating KIRs) among leukemia patients compared to healthy siblings. Results of the phase 2 familial study observed an association between HLA-C1+/BBw4+/ABw4+ haplotype (a mediator of inhibitory signals) and leukemia. Also, we concluded that the absence of HLA-ABw4 alleles was related to leukemia development.

Impact of HLA Allele-KIR Pairs on Disease Outcome in HIV-Infected Thai Population

BACKGROUND

Class I human leukocyte antigen (HLA) molecules contribute to HIV control through antigen presentation to both cytotoxic T lymphocytes and natural killer cells. Contribution of cytotoxic T lymphocytes to HIV clinical outcome by HLA alleles has been well studied. However, reports about the role of natural killer cells in HIV clinical outcome, particularly, about the effect of HLA-killer immunoglobulin-like receptor (KIR) pairs, remain incomplete.

METHODS

The effects of HLA allele-KIR pairs on HIV clinical outcome were statistically analyzed in a Thai cohort of treatment-naive chronically infected population (n = 209).

RESULTS

Five HLA allele-KIR pairs scored significantly in viral load (VL) differences. Among them, opposing effects on VL were identified among subjects expressing KIR2DL2 ligands within the HLA-C1 group: higher VL in individuals expressing HLA-B*46:01+KIR2DL2+ compared with individuals without KIR (HLA-B*46:01+KIR2DL2-) (5.0 vs 4.6 log10 copies/mL, P = 0.02), in HLA-C*01:02+KIR2DL2+ (5.0 vs 4.6 log10 copies/mL; P = 0.02), and lower VL in HLA-C*12:03+KIR2DL2+ (4.3 vs 5.6 log10 copies/mL; P = 0.01). In the longitudinal analysis of a ten-year follow-up, HLA-B*46:01+KIR2DL2+ve subjects also had a higher mortality rate compared with the subjects without that pair, independent of variables including antiretroviral treatment, as well as CD4 T-cell count, sex, and age (adjusted hazard ratio 5.9, P = 0.02).

CONCLUSION

We identified several HLA allele-KIR pairs associated with clinical outcome differences including opposing effects on VL within 1 HLA group with the same KIR. Among them, HLA-B*46:01 emerged in Southeast Asia about 50,000 years ago and is now the most prevalent HLA-B allele in that area. These findings highlight that each endemic area has unique features of anti-HIV innate immunity that impact clinical outcome.

HLA-B locus products resist degradation by the human cytomegalovirus immunoevasin US11

To escape CD8+ T-cell immunity, human cytomegalovirus (HCMV) US11 redirects MHC-I for rapid ER-associated proteolytic degradation (ERAD). In humans, classical MHC-I molecules are encoded by the highly polymorphic HLA-A, -B and -C gene loci. While HLA-C resists US11 degradation, the specificity for HLA-A and HLA-B products has not been systematically studied. In this study we analyzed the MHC-I peptide ligands in HCMV-infected cells. A US11-dependent loss of HLA-A ligands was observed, but not of HLA-B. We revealed a general ability of HLA-B to assemble with β₂m and exit from the ER in the presence of US11. Surprisingly, a low-complexity region between the signal peptide sequence and the Ig-like domain of US11, was necessary to form a stable interaction with assembled MHC-I and, moreover, this region was also responsible for changing the pool of HLA-B ligands. Our data suggest a two-pronged strategy by US11 to escape CD8+ T-cell immunity, firstly, by degrading HLA-A molecules, and secondly, by manipulating the HLA-B ligandome.

The human immune system can cover the presentation of a wide array of pathogen derived antigens owing to the three extraordinary polymorphic MHC class I (MHC-I) gene loci, called HLA-A, -B and -C in humans. Studying the HLA peptide ligands of human cytomegalovirus (HCMV) infected cells, we realized that the HCMV encoded glycoprotein US11 targeted different HLA gene products in distinct manners. More than 20 years ago the first HCMV encoded MHC-I inhibitors were identified, including US11, targeting MHC-I for proteasomal degradation. Here, we describe that the prime target for US11-mediated degradation is HLA-A, whereas HLA-B can resist degradation. Our further mechanistic analysis revealed that US11 uses various domains for distinct functions. Remarkably, the ability of US11 to interact with assembled MHC-I and modify peptide loading of degradation-resistant HLA-B was dependent on a low-complexity region (LCR) located between the signal peptide and the immunoglobulin-like domain of US11. To redirect MHC-I for proteasomal degradation the LCR was dispensable. These findings now raise the intriguing question why US11 has evolved to target HLA-A and -B differentially. Possibly, HLA-B molecules are spared in order to dampen NK cell attack against infected cells.

HLA-F on Autologous HIV-Infected Cells Activates Primary NK Cells Expressing the Activating Killer Immunoglobulin-Like Receptor KIR3DS1

HIV-exposed seronegative KIR3DS1 homozygotes have a reduced risk of HIV infection. HLA-F is the ligand for the activating NK cell receptor (NKR) KIR3DS1. HLA-F is expressed on HIV-infected CD4 T cells. Coculture of sorted, HIV-infected CD4^- (siCD4^-) T cells with NK cells activated a higher frequency of KIR3DS1⁺ than KIR3DS1^- NK cells from KIR3DS1 homozygotes to elicit anti-HIV functions such as CCL4, gamma interferon (IFN-γ), and CD107a expression. This was the case whether KIR3DS1^+/- NK cells were analyzed inclusively or exclusively by gating out NK cells coexpressing the NKRs, KIR2DL1/L2/L3, 3DL2, KIR2DS1/S2/S3/S5, NKG2A, and ILT2. Blocking the interaction of HLA-F on siCD4^- cells with KIR3DS1 on exclusively gated KIR3DS1⁺ NK cells with KIR3DS1-Fc chimeric protein or an HLA-F-specific monoclonal antibody reduced the frequency of activated KIR3DS1⁺ cells compared to that under control conditions. KIR3DS1⁺ NK cell activation by HIV-infected CD4⁺ cells may underlie the reduced risk of KIR3DS1 homozygotes to HIV infection.IMPORTANCE This study investigated a mechanism that may underly epidemiological studies showing that carriage of the KIR3DS1 homozygous genotype is more frequent among HIV-exposed seronegative subjects than among HIV-susceptible individuals. Carriage of this genotype is associated with a reduced risk of HIV infection. The protective mechanism involves the interaction of HLA-F on CD4⁺ cells infected with replication-competent HIV with the activating NK receptor, KIR3DS1. This interaction leads to the activation of KIR3DS1⁺ NK cells for secretion of cytokines and chemokines with anti-HIV activity. Among these is CCL4, which binds and blocks CCR5, the coreceptor for HIV entry of HIV into new target cells. In the setting of an exposure to HIV, incoming HIV-infected cells expressing HLA-F rapidly activate KIR3DS1⁺ NK cells to elicit anti-HIV activity. Exclusive gating strategies and blocking experiments support the notion that the HLA-F/KIR3DS1 interaction is sufficient to activate NK cell functions.

The association of HLA/KIR genes with non-small cell lung cancer (adenocarcinoma) in a Han Chinese population

The host immune system plays a crucial role in the surveillance, recognition and elimination of tumor cells. Recent studies found that Human lymphocyte antigen class I (HLA I) genes, Killer cell immunoglobulin-like receptor (KIR) genes and HLA/KIR combinations play a role in the defense against tumor cells. To evaluated the associations between HLA I genes, KIR genes and HLA/KIR combinations and non-small cell lung cancer (NSCLC) in a Chinese Han population, a total of 229 patients with NSCLC (adenocarcinoma) and 217 healthy individuals were studied. Our results showed that the HLA-C*08:01 allele occurred at a significantly higher frequency in the NSCLCs compared with the controls (P=0.034). The HLA haplotype frequencies bearing HLA-A, -B, and -C loci between the NSCLC and control groups were not different (P>0.05). And there were no differences in the KIR gene, genotype and haplotype frequencies between the NSCLC and control groups (P>0.05). Also, there were no differences between the HLA/KIR combinations in the KIR3D genes and HLA-A3/A11, HLA-Bw4 ligands and KIR2D genes and HLA-C1/C2 ligands between the NSCLC and control groups (P>0.05). Our results indicate that the HLA-C*08:01 allele could be a risk factor for NSCLC (adenocarcinoma) in the Chinese Han population (OR=2.395; 95% CI: 1.359-4.221).

Certain Killer Immunoglobulin-Like Receptor (KIR)/KIR HLA Class I Ligand Genotypes Influence Natural Killer Antitumor Activity in Myelogenous Leukemia but Not in Acute Lymphoblastic Leukemia: A Case Control Leukemia Association Study

Objective:

Natural killers (NK) cell function is mainly controlled by the expression of killer immunoglobulin-like receptors (KIRs) and their ligation with the corresponding ligands. The objective of this study was to investigate the putative association of KIRs, HLA class I ligands, and KIR/ligand combinations with rates of development of acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), and chronic myeloid leukemia (CML).

Materials and Methods:

The KIR/HLA I genotypes of 82 patients with leukemia (ALL, n=52; AML, n=17; and CML, n=13) were determined by PCR-SSP method and compared with genotypes of healthy controls (n=126).

Results:

KIR genotype frequency differed significantly between myelogenous leukemia patients and healthy controls for KIR2DL5A (17.6% vs. 47.7%, p=0.02), KIR3DS1 (17.6% vs. 47.6%, p=0.02), and KIR2DS4*001 (36.6% vs. 20.2%, p=0.017). The incidence of homozygous HLA-BBw4 (31.0% vs. 12.5%, p=0.042) and HLA-Bw4Thr80 Thr80 (13.0% vs. 1.2%, p=0.01) was significantly elevated in myeloid leukemia patients compared to healthy controls. KIR/HLA class I ligand profile KIR3DS1(+)/L (-) was decreased and KIR3DL2(+)/HLA-A3/11(-) was increased among myeloid leukemia cases compared to controls.

Conclusion:

These data suggest that the activity of NK cells as determined by inherited KIR/HLA class I ligand polymorphisms influences the susceptibility to myelogenous leukemia, but not to lymphoblastic leukemia. Additionally, the KIR genotype characterized by the absence of the inhibitory KIR2DL2 and the activating KIR2DS2 and KIR2DS3 (ID2) was found at a lower frequency in patients compared to controls, which confirmed the need for complex analysis based on all possible KIR/HLA class I ligand polymorphism combinations.

KIR specificity and avidity of standard and unusual C1, C2, Bw4, Bw6 and A3/11 amino acid motifs at entire HLA:KIR interface between NK and target cells, the functional and evolutionary classification of HLA class I molecules

Natural killer (NK) cells make vital contributions to the immune system and the reproductive system. Notably, NK cells of donor origin can recognize and kill residual leukaemic cells and cure malignant patients in hematopoietic stem cell (HSC) transplant setting. NK cell function is regulated by KIRs that recognize cognate HLA class I molecules on target cells, depending on their amino acid residues. In review, we addressed the question of binding capacity and avidity of HLA class I molecules to different killer cell immunoglobulin-like receptors (KIRs) depending on all interacting amino acid residues both on HLA and KIR side. We searched PubMed database and analysed available HLA:KIR crystallographic data for amino acid residues in HLA molecules, those physically involved in binding KIRs (termed here the "entire KIR interface"). Within entire KIR interface, we selected five functional sequence motifs (14-19, 66-76, 77-84, 88-92 and 142-151) and classified them according to the conservation of their amino acid sequences among 8,942 HLA class I molecules. Although some conserved amino acid motifs were shared by different groups of KIR ligands, the HLA motif combinations were exclusive for the ligand groups. In 135 common HLA class I molecules with known HLA:KIR recognition, we found 54 combinations of five motifs in each of the KIR-binding interfaces (C1, C2, Bw4, A3/11) and conserved non-KIR-binding interfaces. Based on the entire KIR interface, this analysis allowed to classify 8,942 HLA class I molecules into KIR specificity groups. This functional and evolutionary classification of entire KIR interfaces provides a tool for unambiguously predicting HLA:KIR interactions for common and those HLA molecules that have not yet been functionally tested. Considering the entire KIR interface in HLA class I molecules, functional interactions of HLA and KIR can be predicted in immune responses, reproduction and allotransplantation. Further functional studies are needed on the HLA:KIR interaction variations caused by the repertoires of peptides presented by HLA molecules and KIR polymorphisms at allelic level.

Killer Ig-Like Receptors (KIRs): Their Role in NK Cell Modulation and Developments Leading to Their Clinical Exploitation

Natural killer (NK) cells contribute to the first line of defense against viruses and to the control of tumor growth and metastasis spread. The discovery of HLA class I specific inhibitory receptors, primarily of killer Ig-like receptors (KIRs), and of activating receptors has been fundamental to unravel NK cell function and the molecular mechanisms of tumor cell killing. Stemmed from the seminal discoveries in early '90s, in which Alessandro Moretta was the major actor, an extraordinary amount of research on KIR specificity, genetics, polymorphism, and repertoire has followed. These basic notions on NK cells and their receptors have been successfully translated to clinical applications, primarily to the haploidentical hematopoietic stem cell transplantation to cure otherwise fatal leukemia in patients with no HLA compatible donors. The finding that NK cells may express the PD-1 inhibitory checkpoint, particularly in cancer patients, may allow understanding how anti-PD-1 therapy could function also in case of HLA class I^neg tumors, usually susceptible to NK-mediated killing. This, together with the synergy of therapeutic anti-checkpoint monoclonal antibodies, including those directed against NKG2A or KIRs, emerging in recent or ongoing studies, opened new solid perspectives in cancer therapy.

Diversity of Killer Cell Immunoglobulin-Like Receptors and Disease

Natural killer (NK) cells are bone marrow-derived large granular lymphocytes defined by CD3^negCD56^pos and represent 5% to 25% of peripheral blood mononuclear cell fraction of the healthy humans. NK cells have a highly specific and sophisticated target cell recognition receptor system arbitrated by the integration of signals triggered by a multitude of inhibitory and activating receptors. Human NK cells express distinct families of receptors, including (1) killer cell immunoglobulin-like receptors, (2) killer cell lectin-like receptors, (3) leukocyte immunoglobulin-like receptors, and (4) natural cytotoxicity receptors.

Impact of HLA Allele-KIR Pairs on HIV Clinical Outcome in South Africa

BACKGROUND

HLA class I contributes to HIV immune control through antigen presentation to cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. In contrast to investigations of CTL, studies of NK cells in HIV control through HLA-killer immunoglobulin-like receptor (KIR) interactions remain sparse in African cohorts.

METHODS

Treatment-naive, chronically HIV-infected adults (N = 312) were recruited from South Africa, and the effects of HLA-KIR pairs on clinical outcome were analyzed.

RESULTS

There was no significant difference in viral load among all subjects with HLA alleles from the HLA-C1 group (P = .1). However, differences in HLA-C type significantly influenced viremia among 247 KIR2DL3 positives (P = .04), suggesting that specific HLA-KIR interactions contribute to immune control. Higher viral load (P = .02) and lower CD4+ T-cell counts (P = .008) were observed in subjects with HLA-C*16:01+KIR2DL3+. Longitudinal analysis showed more rapid progression to AIDS among HLA-C*16:01+KIR2DL3+ subjects (adjusted hazard ratio 1.9, P = .03) than those without this genotype, independent of CD4+ T-cell count and viral load.

CONCLUSIONS

These results highlight the existence of unique anti-HIV innate immunity within distinct populations and the contribution of KIR on NK cells and some CTLs to the well-described HLA-mediated impact on HIV disease progression.

Diversity of KIR, HLA Class I, and Their Interactions in Seven Populations of Sub-Saharan Africans

HLA class I and KIR sequences were determined for Dogon, Fulani, and Baka populations of western Africa, Mbuti of central Africa, and Datooga, Iraqw, and Hadza of eastern Africa. Study of 162 individuals identified 134 HLA class I alleles (41 HLA-A, 60 HLA-B, and 33 HLA-C). Common to all populations are three HLA-C alleles (C1⁺C*07:01, C1⁺C*07:02, and C2⁺C*06:02) but no HLA-A or -B Unexpectedly, no novel HLA class I was identified in these previously unstudied and anthropologically distinctive populations. In contrast, of 227 KIR detected, 22 are present in all seven populations and 28 are novel. A high diversity of HLA A-C-B haplotypes was observed. In six populations, most haplotypes are represented just once. But in the Hadza, a majority of haplotypes occur more than once, with 2 having high frequencies and 10 having intermediate frequencies. The centromeric (cen) part of the KIR locus exhibits an even balance between cenA and cenB in all seven populations. The telomeric (tel) part has an even balance of telA to telB in East Africa, but this changes across the continent to where telB is vestigial in West Africa. All four KIR ligands (A3/11, Bw4, C1, and C2) are present in six of the populations. HLA haplotypes of the Iraqw and Hadza encode two KIR ligands, whereas the other populations have an even balance between haplotypes encoding one and two KIR ligands. Individuals in these African populations have a mean of 6.8-8.4 different interactions between KIR and HLA class I, compared with 2.9-6.5 for non-Africans.

Two to Tango: Co-evolution of Hominid Natural Killer Cell Receptors and MHC

Natural killer (NK) cells have diverse roles in hominid immunity and reproduction. Modulating these functions are the interactions between major histocompatibility complex (MHC) class I molecules that are ligands for two NK cell surface receptor types. Diverse killer cell immunoglobulin-like receptors (KIR) bind specific motifs encoded within the polymorphic MHC class I cell surface glycoproteins, while, in more conserved interactions, CD94:NKG2A receptors recognize MHC-E with bound peptides derived from MHC class I leader sequences. The hominid lineage presents a choreographed co-evolution of KIR with their MHC class I ligands. MHC-A, -B, and -C are present in all great apes with species-specific haplotypic variation in gene content. The Bw4 epitope recognized by lineage II KIR is restricted to MHC-B but also present on some gorilla and human MHC-A. Common to great apes, but rare in humans, are MHC-B possessing a C1 epitope recognized by lineage III KIR. MHC-C arose from duplication of MHC-B and is fixed in all great apes except orangutan, where it exists on approximately 50% of haplotypes and all allotypes are C1-bearing. Recent study showed that gorillas possess yet another intermediate MHC organization compared to humans. Like orangutans, but unlike the Pan-Homo species, duplication of MHC-B occurred. However, MHC-C is fixed, and the MHC-C C2 epitope (absent in orangutans) emerges. The evolution of MHC-C drove expansion of its cognate lineage III KIR. Recently, position −21 of the MHC-B leader sequence has been shown to be critical in determining NK cell educational outcome. In humans, methionine (−21M) results in CD94:NKG2A-focused education whereas threonine (−21T) produces KIR-focused education. This is another dynamic position among hominids. Orangutans have exclusively −21M, consistent with their intermediate stage in lineage III KIR-focused evolution. Gorillas have both −21M and −21T, like humans, but they are unequally encoded by their duplicated B genes. Chimpanzees have near-fixed −21T, indicative of KIR-focused NK education. Harmonious with this observation, chimpanzee KIR exhibit strong binding and, compared to humans, smaller differences between binding levels of activating and inhibitory KIR. Consistent between these MHC-NK cell receptor systems over the course of hominid evolution is the evolution of polymorphism favoring the more novel and dynamic KIR system.

Natural Killer Cell Education Is Associated With a Distinct Glycolytic Profile

NK cells expressing self-inhibitory receptors display increased functionality compared to NK cells lacking those receptors. The acquisition of functional competence in these particular NK-cell subsets is termed education. Little is known about the underlying mechanisms that lead to the functional differences between educated and uneducated NK cells. An increasing number of studies suggest that cellular metabolism is a determinant of immune cell functions. Thus, alterations in cellular metabolic pathways may play a role in the process of NK-cell education. Here, we compared the glycolytic profile of educated and uneducated primary human NK cells. KIR-educated NK cells showed significantly increased expression levels of the glucose transporter Glut1 in comparison to NKG2A-educated or uneducated NK cells with and without exposure to target cells. Subsequently, the metabolic profile of NK-cell subsets was determined using a Seahorse XF Analyzer. Educated NK cells displayed significantly higher rates of cellular glycolysis than uneducated NK cells even in a resting state. Our results indicate that educated and uneducated NK cells reside in different metabolic states prior to activation. These differences in the ability to utilize glucose may represent an underlying mechanism for the superior functionality of educated NK cells expressing self-inhibitory receptors.

Inhibitory natural killer cell receptor KIR3DL1 with its ligand Bw4 constraints HIV-1 disease among South Indians

OBJECTIVE

To investigate the role of genotypic and phenotypic characteristics of killer cell immunoglobulin-like receptors (KIRs) and their human leukocyte antigen (HLA) class-1 ligands in HIV-1 disease progression.

STUDY DESIGN AND METHODS

This is a nested case-control study including 347 HIV seropositive (HIV-1+) individuals from South India constituting 45 long-term nonprogressors (LTNPs) and 302 disease progressors. KIR genotyping was performed by multiplex sequence-specific primer-directed PCR (SSP-PCR). Phenotypic expressions of KIR3DL1/S1 was studied using multiparametric flow cytometry assay. HLA-Bw4 and Bw6 epitopes were determined by ARMS-PCR. HLA-Bw4I80, HLA-Bw4T80, HLA-C1, HLA-C2, and HLA-Aw4 were genotyped using SSP-PCR. Serum levels of IFN-γ was quantified using ELISA method.

RESULTS

Overall, 37 different KIR genotypes were observed and the distribution of genotypes with AB-AB (OR = 2.2, P = 0.033) constellations showed significant increase among LTNPs. The frequencies of 3DL1-2DL3-2DL5 (OR = 2.2, Pc = 0.031), 3DL1-Bw4/Aw4 (OR = 2.49, Pc = 0.019), homozygous Bw4 (OR = 2.422, Pc = 0.011) were observed higher in LTNPs and 2DS1-2DS2-2DS3 (OR =  0.475, Pc = 0.03), homozygous Bw6 (OR = 0.413, Pc = 0.011) were higher in the disease progressors. Flow cytometry assay showed the increased expression and maintenance of 3DL1/S1+NK cells in LTNPs (P = 0.0001). Further the expansion of 3DS1+NK cells was higher than 3DL1+NK cells in the heterozygous 3DL1/S1 LTNPs (P = 0.001).

CONCLUSION

The inhibitory receptor 3DL1 with Bw4 and its A-haplotype defining KIR genes (2DL3/L5) confers protection against HIV-1 disease progression. An increased expression and maintenance of 3DL1/S1+ natural killer cells may contribute to the efficient activation of the natural killer cells and subsequent long-term nonprogression (LTNPn) to the disease.