Killer cell immunoglobulin-like receptor gene-cluster 3DS1-2DL5-2DS1-2DS5 predisposes susceptibility to Vogt-Koyanagi-Harada syndrome in Japanese individuals

The Role of Killer Ig-like Receptors in Diseases from A to Z

Killer Ig-like Receptors (KIRs) regulate immune responses, maintaining the balance between activation and inhibition of the immune system. KIRs are expressed on natural killer cells and some CD8 T cells and interact with HLA class I molecules, influencing various physiological and pathological processes. KIRs' polymorphism creates a variability in immune responses among individuals. KIRs are involved in autoimmune disorders, cancer, infections, neurological diseases, and other diseases. Specific combinations of KIRs and HLA are linked to several diseases' susceptibility, progression, and outcomes. In particular, the balance between inhibitory and activating KIRs can determine how the immune system responds to pathogens and tumors. An imbalance can lead to an excessive response, contributing to autoimmune diseases, or an inadequate response, allowing immune evasion by pathogens or cancer cells. The increasing number of studies on KIRs highlights their essential role as diagnostic and prognostic biomarkers and potential therapeutic targets. This review provides a comprehensive overview of the role of KIRs in all clinical conditions and diseases, listed alphabetically, where they are analyzed.

Identification of immune hub genes participating in the pathogenesis and progression of Vogt-Koyanagi-Harada disease

Background

Vogt-Koyanagi-Harada (VKH) disease is an autoimmune inflammatory disorder characterized by bilateral granulomatous uveitis. The objective of this study was to identify immune hub genes involved in the pathogenesis and progression of VKH disease.

Methods

High throughput sequencing data were downloaded from the Gene Expression Omnibus (GEO) and an immune dataset was downloaded from ImmPort. Immune differentially expressed genes (DEGs) were obtained from their intersection in the GEO and ImmPort datasets. Immune hub genes for VKH disease were selected through differential expression analyses, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Disease Ontology (DO), protein-protein interaction (PPI) network, and clustering analyses. Confidence in the immune hub genes was subsequently validated using box plots and receiver operating characteristic (ROC) curves.

Results

A total of 254 DEGs were screened and after the intersection with ImmPort, 20 genes were obtained as immune DEGs. Functional enrichment analysis indicated that the key genes were mainly involved in several types of immune pathways (such as the lymphocyte mediated and leukocyte mediated immune responses, natural killer cell mediated cytotoxicity, and antigen binding) and immunodeficiency diseases. Following PPI network analysis, the top seven genes in cluster 1 were selected as potential immune hub genes in VKH. After evaluating the accuracy of the hub genes, one gene (GNLY) was excluded because its expression level was statistically similar in VKH patients and healthy controls. Finally, six immune hub genes, namely KLRC2, KLRC3 SH2D1B, GZMB, KIR2DL3, and KIR3DL2 were identified as playing important roles in the occurrence and development of VKH disease.

Conclusion

Six immune hub genes (KLRC2, KLRC3 SH2D1B, GZMB, KIR2DL3, and KIR3DL2) identified by our bioinformatics analyses may provide new diagnostic and therapeutic targets for VKH disease.

Pathogenesis of Non-Infectious Uveitis Elucidated by Recent Genetic Findings

Uveitis is a generic term for inflammation of the uvea, which includes the iris, ciliary body, and choroid. Prevalence of underlying non-infectious uveitis varies by race and region and is a major cause of legal blindness in developed countries. Although the etiology remains unclear, the involvement of both genetic and environmental factors is considered important for the onset of many forms of non-infectious uveitis. Major histocompatibility complex (MHC) genes, which play a major role in human immune response, have been reported to be strongly associated as genetic risk factors in several forms of non-infectious uveitis. Behçet’s disease, acute anterior uveitis (AAU), and chorioretinopathy are strongly correlated with MHC class I-specific alleles. Moreover, sarcoidosis and Vogt-Koyanagi-Harada (VKH) disease are associated with MHC class II-specific alleles. These correlations can help immunogenetically classify the immune pathway involved in each form of non-infectious uveitis. Genetic studies, including recent genome-wide association studies, have identified several susceptibility genes apart from those in the MHC region. These genetic findings help define the common or specific pathogenesis of ocular inflammatory diseases by comparing the susceptibility genes of each form of non-infectious uveitis. Interestingly, genome-wide association of the interleukin (IL)23R region has been identified in many of the major forms of non-infectious uveitis, such as Behçet’s disease, ocular sarcoidosis, VKH disease, and AAU. The interleukin-23 (IL-23) receptor, encoded by IL23R, is expressed on the cell surface of Th17 cells. IL-23 is involved in the homeostasis of Th17 cells and the production of IL-17, which is an inflammatory cytokine, indicating that a Th17 immune response is a common key in the pathogenesis of non-infectious uveitis. Based on the findings from the immunogenetics of non-infectious uveitis, a personalized treatment approach based on the patient’s genetic make-up is expected.

Vogt-Koyanagi-Harada patients show higher frequencies of circulating NKG2Dpos NK and NK T cells

Vogt-Koyanagi-Harada (VKH) is an autoimmune disease characterized by inflammation in tissues that contain melanocytes. We aimed to increase the knowledge regarding immunological pathways deregulated in VKH disease. We compared the percentages of circulating natural killer (NK), NK T and T cells expressing the activatory markers: CD16, CD69, NK group 2D (NKG2D), natural cytotoxicity triggering receptor 3 (Nkp30), natural cytotoxicity triggering receptor 1 (Nkp46) and the inhibitory marker: NK group 2 member A (NKG2A) in 10 active VKH patients, 20 control subjects (CTR) and seven patients with Behçet disease (BD) by flow cytometry. Cytotoxic potential of NK cells was determined through the degranulation marker CD107a expression after contact with K562 cells by flow cytometry. Moreover, plasmatic levels of 27 cytokines were determined with a multiplex bead-based assay. VKH patients showed higher percentages of NKG2D^pos NK and NK T cells versus CTR. The cytotoxic potential of NK cells induced by K562 cells was comparable between VKH patients and CTR. Finally, higher concentrations of interleukin (IL)-4, IL-5, IL-7, IL-17 and platelet-derived growth factor-subunits B (PDGF-bb) were detected in plasma of VKH patients versus CTR. The immune profile of VKH patients was similar to that of BD patients.

Autoimmune vertigo: an update on vestibular disorders associated with autoimmune mechanisms

The role of the immune system in mediating cochleovestibular pathologies has received increasing attention in recent years. Autoimmune vertigo may be an invalidating condition and may worsen the quality of life of affected patients, especially in the cases of delayed diagnosis. Since the etiopathogenesis is still not clear, also the treatment is not yet completely delineated. According to the clinical presentation, autoimmune vertigo can present as an isolated disorder or in association with systemic autoimmune diseases. The main feature in autoimmune vertigo is the presence of an abnormal immune response, in either absence or presence of systemic autoimmune disease, directed against delicate components of the inner ear. This may determine a functional or anatomical alteration, with an inflammatory reaction often devastating for hearing and balance. Being the exact pathogenesis unknown, the diagnosis of autoimmune vertigo is based either on clinical criteria or on a positive response to steroids. The earlier the diagnosis is made, the sooner the therapy can be installed, giving a chance to the recovery of inner ear damages. Corticosteroids represent the most effective and universally accepted treatment, even if other immunomodulatory drugs are now having a more extensive use. HIGHLIGHTS: Vertigo is relatively frequent in autoimmune diseases; however, it is often misdiagnosed or attributed to central nervous system alterations rather to specific inner ear involvement. Vertigo and other audiovestibular symptoms may be the first manifestation of an autoimmune disease and if correctly addressed could significantly contribute to early diagnosis of the underlying autoimmune disease. Early diagnosis of immune-related vertigo can lead to prompt initiation of targeted therapy with elevate chances of preventing irreversible damages to the inner ear. The presence of alternating phases of well-being and disabling symptoms in patients with vertigo should always been considered, as they could suggest an underlying autoimmune condition.

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.

Association of human leukocyte antigen (HLA)-DQ and HLA-DQA1/DQB1 alleles with Vogt-Koyanagi-Harada disease: A systematic review and meta-analysis

OBJECTIVE

The aim of this study was to evaluate the association of human leukocyte antigen (HLA)-DQ and HLA-DQA1/DQB1 alleles with Vogt-Koyanagi-Harada (VKH), providing further evidences on the genetic background of this disease.

METHODS

A comprehensive literature search was conducted on the relationship of HLA-DQ and/or HLA-DQA1/DQB1 alleles with VKH through PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, VIP, and databases for grey literature. The last search was in October 2017. Pooled odds ratio (OR) with 95% confidence interval (95% CI) was calculated from extracted data to access the strength of the association between a genotype and VKH.

RESULTS

HLA-DQ4 was confirmed to increase the risk of VKH significantly (OR = 4.63, 95% CI: 1.74-12.31, P = .002), while HLA-DQ1 seemed to reduce VKH occurrence with OR = 0.32 (95% CI: 0.22-0.47, P < .00001). HLA-DQA1*0301-(OR = 4.52, 95% CI: 1.42-14.35, P = .01) and HLA-DQB1*0401-(OR = 23.12, 95% CI: 11.54-46.31, P < .00001) positive patients probably had a rising tendency to suffer from VKH. Alleles including HLA-DQA1*0103, 0401, 0501 and HLA-DQB1*0301, 0402, 0601, 0603 were significant protective genetic factors.

CONCLUSION

We concluded that HLA-DQ4 carriers had a higher risk of VKH and HLA-DQ1 seemed to be protective. People with positive HLA-DQA1*0301 and HLA-DQB1*0401 demonstrated to be more susceptible to VKH. HLA-DQA1*0103, 0401, 0501 and HLA-DQB1*0301, 0402, 0601, 0603 could be potential protectors.

Ocular toxoplasmosis: susceptibility in respect to the genes encoding the KIR receptors and their HLA class I ligands

The objective of this study was to investigate the influence of the genes encoding the KIR receptors and their HLA ligands in the susceptibility of ocular toxoplasmosis. A total of 297 patients serologically-diagnosed with toxoplasmosis were selected and stratified according to the presence (n = 148) or absence (n = 149) of ocular scars/lesions due to toxoplasmosis. The group of patients with scars/lesions was further subdivided into two groups according to the type of ocular manifestation observed: primary (n = 120) or recurrent (n = 28). Genotyping was performed by PCR-SSOP. Statistical analyses were conducted using the Chi-square test, and odds ratio with a 95% confidence interval was also calculated to evaluate the risk association. The activating KIR3DS1 gene was associated with increased susceptibility for ocular toxoplasmosis. The activating KIR together with their HLA ligands (KIR3DS1-Bw4-80Ile and KIR2DS1⁺/C2⁺⁺ KIR3DS1⁺/Bw4-80Ile⁺) were associated with increased susceptibility for ocular toxoplasmosis and its clinical manifestations. KIR-HLA inhibitory pairs -KIR2DL3/2DL3-C1/C1 and KIR2DL3/2DL3-C1- were associated with decreased susceptibility for ocular toxoplasmosis and its clinical forms, while the KIR3DS1⁻/KIR3DL1⁺/Bw4-80Ile⁺ combination was associated as a protective factor against the development of ocular toxoplasmosis and, in particular, against recurrent manifestations. Our data demonstrate that activating and inhibitory KIR genes may influence the development of ocular toxoplasmosis.

Killer Immunoglobulin-Like Receptor Profiles Are not Associated with Risk of Amoxicillin-Clavulanate-Induced Liver Injury in Spanish Patients

Natural killer cells are an integral part of the immune system and represent a large proportion of the lymphocyte population in the liver. The activity of these cells is regulated by various cell surface receptors, such as killer Ig-like receptors (KIR) that bind to human leukocyte antigen (HLA) class I ligands on the target cell. The composition of KIR receptors has been suggested to influence the development of specific diseases, in particularly autoimmune diseases, cancer and reproductive diseases. The role played in idiosyncratic drug-induced liver injury (DILI) is currently unknown. In this study, we examined KIR gene profiles and HLA class I polymorphisms in amoxicillin-clavulanate (AC) DILI patients in search for potential risk associations. One hundred and two AC DILI patients and 226 controls were genotyped for the presence or absence of 16 KIR loci, including the two pseudogenes 2DP1 and 3DP1. No significant differences were found in the distribution of individual KIRs between patients and controls, which were comparable to previously reported KIR data from ethnically similar cohorts. The 21.6 and 21.2% of the patients and controls, respectively, were homozygous haplotype A carriers, while 78.4 and 78.8%, respectively, contained at least one B haplotype (Bx). The genotypes translated into 27 (AC DILI) and 46 (controls) different gene profiles, with 19 being present in both groups. The most frequent Bx gene profile containing KIRs 2DS2, 2DL2, 2DL3, 2DP1, 2DL1, 3DL1, 2DS4, 3DL2, 3DL3, 2DL4, and 3PD1 was present in 16% of the DILI patients and 14% of the controls. The distribution of HLA class I epitopes did not differ significantly between AC DILI patients and controls. The most frequent receptor-ligand combinations in the DILI patients were 2DL3 + epitope C1 (67%) and 3DL1 + Bw4 motif (67%), while 2DL1 + epitope C2 (69%) and 3DL1 + Bw4 motif (69%) predominated in the controls. This is to our knowledge the first analysis of KIR receptor-HLA ligand associations in DILI, although our findings do not support evidence of these genetic variations playing a major role in AC DILI development.

KIR and HLA Genotypes Implicated in Reduced Killer Lymphocytes Immunity Are Associated with Vogt-Koyanagi-Harada Disease

Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells are killer lymphocytes that provide defense against viral infections and tumor transformation. Analogous to that of CTL, interactions of killer-cell immunoglobulin-like receptors (KIR) with specific human leukocyte antigen (HLA) class I ligands calibrate NK cell education and response. Gene families encoding KIRs and HLA ligands are located on different chromosomes, and feature variation in the number and type of genes. The independent segregation of KIR and HLA genes results in variable KIR-HLA interactions in individuals, which may impact disease susceptibility. We tested whether KIR-HLA combinations are associated with Vogt-Koyanagi-Harada (VKH) disease, a bilateral granulomatous panuveitis that has strong association with HLA-DR4. We present a case control study of 196 VKH patients and 209 controls from a highly homogeneous native population of Japan. KIR and HLA class I genes were typed using oligonucleotide hybridization method and analyzed using two-tailed Fisher’s exact probabilities. The incidence of Bx-KIR genotypes was decreased in VKH patients (odds ratio [OR] 0.58, P = 0.007), due primarily to a decrease in centromeric B-KIR motif and its associated KIRs 2DS2, 2DL2, 2DS3, and 2DL5B. HLA-B22, implicated in poor immune response, was increased in VKH (OR = 4.25, P = 0.0001). HLA-Bw4, the ligand for KIR3DL1, was decreased in VKH (OR = 0.59, P = 0.01). The KIR-HLA combinations 2DL2+C1/C2 and 3DL1+Bw4, which function in NK education, were also decreased in VKH (OR = 0.49, P = 0.012; OR = 0.59, P = 0.013). Genotypes missing these two inhibitory KIR-HLA combinations in addition to missing activating KIRs 2DS2 and 2DS3 were more common in VKH (OR = 1.90, P = 0.002). These results suggest that synergistic hyporesponsiveness of NK cells (due to poor NK education along with missing of activating KIRs) and CTL (due to HLA-B22 restriction) fail to mount an effective immune response against viral-infection that may trigger VKH pathogenesis in genetically susceptible individuals, such as HLA-DR4 carriers.

Vogt-Koyanagi-Harada disease: Novel insights into pathophysiology, diagnosis and treatment

Vogt-Koyanagi-Harada (VKH) disease is one of the major vision-threatening diseases in certain populations, such as Asians, native Americans, Hispanics and Middle Easterners. It is characterized by bilateral uveitis that is frequently associated with neurological (meningeal), auditory, and integumentary manifestations. Although the etiology and pathogenesis of VKH disease need to be further elucidated, it is widely accepted that the clinical manifestations are caused by an autoimmune response directed against melanin associated antigens in the target organs, i.e. the eye, inner ear, meninges and skin. In the past decades, accumulating evidence has shown that genetic factors, including VKH disease specific risk factors (HLA-DR4) and general risk factors for immune mediated diseases (IL-23R), dysfunction of immune responses, including the innate and adaptive immune system and environmental triggering factors are all involved in the development of VKH disease. Clinically, the criteria of diagnosis for VKH disease have been further improved by the employment of novel imaging techniques for the eye. For the treatment, early and adequate corticosteroids are still the mainstream regime for the disease. However, immunosuppressive and biological agents have shown benefit for the treatment of VKH disease, especially for those patients not responding to corticosteroids. This review is focused on our current knowledge of VKH disease, especially for the diagnosis, pathogenesis (genetic factors and immune mechanisms), ancillary tests and treatment. A better understanding of the role of microbiome composition, genetic basis and ongoing immune processes along with the development of novel biomarkers and objective quantitative assays to monitor intraocular inflammation are needed to improve current management of VKH patients.

The Relationship Between Killer Cell Immunoglobulin-Like Receptors and HLA-C Polymorphisms in Colorectal Cancer in a Saudi Population

AIMS

We performed an association study to evaluate the contribution of 16 killer cell immunoglobulin-like receptor (KIR) genotype polymorphisms and the HLA-C1 and -C2 ligands in the development of colorectal cancer (CRC) in Saudi Arabian patients.

METHODS

A total of 52 patients with different stages of malignant CRC as well as 70 healthy Saudi controls were enrolled at the King Khalid University Hospital.

RESULTS

Our results showed that the frequency of the activating mutations KIR2DS1, 2DS2, 2DS3, 2DS5, and 3DS1 was significantly higher in CRC patients compared to controls. The 3DS1 gene contributed to the highest risk of CRC (odds ratio [OR] = 16.25, p < 0.0001), followed by 2DS1 (OR = 8.6; p < 0.0001). The distributions of HLA-C1 and -C2 ligands were not significantly different between patients and controls. Analyses of different combinations of KIR genes with their HLA-C1 and -C2 ligands show that the frequency of 2DL3 in the presence of its ligand, the allotype C1, was significantly more prevalent in patients compared to controls. In addition, 2DL2 and 2DL3 that were aggregated in combination with the ligand, HLA-C1, were found to be more highly associated mainly with the homozygote HLA-C1/C1 (p = 0.03; OR = 2.6). The activating mutations 2DS1 and 2DS2 when combined with their respective ligands, HLA-C2 and -C1, showed highly significant associations with CRC development.

CONCLUSION

This study supports a key role for KIR gene mutations in the development of CRC, especially in association with their ligands.

Influence of molecular genetics in Vogt-Koyanagi-Harada disease

Vogt-Koyanagi-Harada (VKH) disease is a systemic autoimmune disorder against melanocytes. Recent studies have identified multiple genetic factors that might be associated with the pathogenesis of VKH disease. We performed an electronic database search of PubMed, MEDLINE, and EMBASE, and all relevant papers published up to 13 June 2014 were reviewed. A total of 1,031 publications including articles relevant to the genetics of VKH disease and the references of these articles were reviewed. The review identified a number of genetic factors which might be involved in the pathogenesis of VKH disease, some of which may alter the clinical course of VKH disease. Genes which might be involved in the pathogenesis of VKH disease included genes expressing HLA, complement factor H, interleukins, cytotoxic T-lymphocyte antigen 4 (CTLA-4), killer cell immunoglobulin-like receptors (KIR), programmed cell death 1 (PDCD1), protein tyrosine phosphatase non-receptor 22 (PTPN22), osteopontin, tumor necrosis factor alpha-induced protein 3 (TNFAIP3), macrophage migration inhibitory factor (MIF), and other immune response genes. Further studies to explore the correlation among different genotypes and phenotypes of VKH disease will be useful to shed light on the pathogenesis of uveitis in VKH disease and may facilitate the development of new treatment modalities of uveitis in VKH disease.

Gene-specific PCR typing of killer cell immunoglobulin-like receptors

By interacting with specific HLA class I molecules, the killer cell immunoglobulin-like receptors (KIR) regulate the effector function of natural killer (NK) cells and subsets of CD8 T cells. The KIR receptors and HLA class I ligands are encoded by unlinked polymorphic gene families located on different human chromosomes, 19 and 6, respectively. The number and type of KIR genes are substantially variable between individuals, which may contribute to human diversity in responding to infection, malignancy and allogeneic transplants. PCR typing using sequence-specific primers (PCR-SSP) is the most commonly used method to determine KIR gene content. This chapter describes a step-by-step protocol for PCR-SSP typing to identify the presence and absence of all 16 known KIR genes. Moreover, the chapter provides the basic rules to verify the accuracy of KIR genotyping results and explains specific methods for the data analysis.

Killer cell immunoglobulin like receptor gene association with tuberculosis

NK cells are vital components of innate immune system and are the first cells which come into picture mediating resistance against intracellular pathogens. NK cell cytotoxicity is modulated by a wide variety of cell surface receptors that recognize and respond towards infected cells. Activation of NK cells are controlled by both inhibitory and activating receptors, encoded by KIR genes and bind to HLA ligands. Not much is known about KIR genes and their influence on the pathogenesis with M. tuberculosis infection. Our study aimed at detecting the presence of 14 KIR genes, their distribution and their association with tuberculosis. Total 77 different genotype combinations were observed which belonged to B-haplotype. Fifteen genotypes were similar to those reported in other world populations while remaining 62 were unique to this study group. Inhibitory genes KIR3DL1, KIR2DL3 and activating genes KIR2DS1, KIR2DS5 conferred susceptibility towards TB either individually or in haplotype combinations. The complimentary MHC ligands need to be tested for the functional relevance of the associated genes.

Killer cell immunoglobulin-like receptor gene polymorphisms predispose susceptibility to Epstein-Barr virus associated hemophagocytic lymphohistiocytosis in Chinese children

Epstein-Barr virus associated hemophagocytic lymphohistiocytosis (EBV-HLH) has a high mortality rate among children. The pathogenesis of, and underlying predisposing factors for, EBV-HLH are as yet unclear; however, natural killer cells may play a key role in progression of the disease. This study attempted to determine whether killer cell immunoglobulin-like receptor (KIR) gene polymorphisms are responsible for susceptibility to EBV-HLH. Of the 125 children with EBV infection studied, 59 had EBV-HLH and 66 patients had EBV associated infectious mononucleosis (IM) without HLH. The control group was 146 normal children without immune deficiency. KIR polymorphisms were determined by polymerase chain reaction with sequence-specific primers. KIR polymorphism data were analyzed using the X(2) test or Fisher's exact test. The overall observed carrier frequency (OF) of KIR2DS5 was significantly higher in EBV-HLH patients than in IM patients and normal controls (49.2% versus 31.8%, P = 0.048; 49.2% versus 31.5%, P = 0.018, respectively), and the odds ratios (95% confidence interval) were 2.071 (1.001-4.286) and 2.101(1.132-3.900) respectively. The OF of KIR3DS1 was significantly higher in the EBV-HLH patients than in the IM patients (47.4% versus 24.6%, P = 0.012), but not different from normal controls. In summary, KIR polymorphisms may be involved in the development of EBV-HLH, with KIR2DS5 promoting susceptibility to this disease. The obtained KIR data will enrich the understanding of genetic relationships among diseases associated with EBV infection in children.

Overview of the killer cell immunoglobulin-like receptor system

Natural killer (NK) cells are more than simple killers and have been implicated in control and clearance of malignant and virally infected cells, regulation of adaptive immune responses, rejection of bone marrow transplants, and autoimmunity and the maintenance of pregnancy. Human NK cells largely use a family of germ-line encoded killer cell immunoglobulin-like receptors (KIR) to respond to the perturbations from self-HLA class I molecules present on infected, malignant, or HLA-disparate fetal or allogenic transplants. Genes encoding KIR receptors and HLA class I ligands are located on different chromosomes, and both feature extraordinary diversity in the number and type of genes. The independent segregation of KIR and HLA gene families produce diversity in the number and type of KIR-HLA gene combinations inherited in individuals, which may determine their immunity and susceptibility to diseases. This chapter provides an overview of NK cells and their unprecedented phenotypic and functional diversity within and between individuals.

Human diversity of killer cell immunoglobulin-like receptors and disease

Natural Killer (NK) cells are the third population of lymphocyte in the mononuclear cell compartment that triggers first-line of defense against viral infection and tumor transformation. Historically, NK cells were thought of as components of innate immunity based on their intrinsic ability to spontaneously kill target cells independent of HLA antigen restriction. However, it is now clear that NK cells are quite sophisticated and use a highly specific and complex target cell recognition receptor system arbitrated via a multitude of inhibitory and activating receptors. Killer cell immunoglobulin-like receptors (KIR) are the key receptors of human NK cells development and function. To date, fourteen distinct KIRs have been identified: eight are inhibitory types, and six are activating types. The number and type of KIR genes present varies substantially between individuals. Inhibitory KIRs recognize distinct motifs of polymorphic HLA class I molecules. Upon engagement of their specific HLA class I ligands, inhibitory KIR dampen NK cell reactivity. In contrast, activating KIRs are believed to stimulate NK cell reactivity when they sense their ligands (unknown). KIR and HLA gene families map to different human chromosomes (19 and 6, respectively), and their independent segregation produces a wide diversity in the number and type of inherited KIR-HLA combinations, likely contributing to overall immune competency. Consistent with this hypothesis, certain combinations of KIR-HLA variants have been correlated with susceptibility to diseases as diverse as autoimmunity, viral infections, and cancer. This review summarizes our emerging understanding of KIR-HLA diversity in human health and disease.

An update on the genetics of HLA B27-associated acute anterior uveitis

The discovery of the association of HLA B27 with spondyloarthropathy led to more questions than answers about the role of this gene in disease susceptibility. The realization that HLA B27 was not responsible for all of the genetic effects helped to lay a foundation for further investigation into the genetics of uveitis. Over several decades, genetic findings have provided clues to advance the understanding of mechanisms of uveitis and to catalyze new research on diagnostics, animal models, and therapies. From the early candidate gene studies on immune mediators to the recent genome-wide investigations, much has been discovered. However, these discoveries have come with the caveat that a genetic finding does not automatically reveal the disease-relevant functional effect of the associated variant.