A distinct distribution of natural killer cell subgroups in human tissues and blood

The causality between CD8+NKT cells and CD16-CD56 on NK cells with hepatocellular carcinoma: a Mendelian randomization study

BACKGROUND

Hepatocellular carcinoma (HCC), which is featured with high morbidity and mortality worldwide, is a primary malignant tumor of the liver. Recently, there is a wealth of supporting evidence revealing that NK cell-related immune traits are strongly associated with the development of HCC, but the causality between them has not been proven.

METHODS

Two-sample Mendelian randomization (MR) study was performed to probe the causal correlation between NK cell-related immune traits and HCC. Genetic variations in NK cell-related immune traits were extracted from recent genome-wide association studies (GWAS) of individuals with European blood lineage. HCC data were derived from the UK Biobank Consortium's GWAS summary count data, including a total of 372,184 female and male subjects, with 168 cases and 372,016 controls, all of whom are of European ancestry. Sensitivity analysis was mainly used for heterogeneity and pleiotropy testing.

RESULTS

Our research indicated the causality between NK cell-related immune traits and HCC. Importantly, CD8+NKT cells had protective causal effects on HCC (OR = 0.9996;95%CI,0.9993-0.9999; P = 0.0489). CD16-CD56 caused similar effects on NK cells (OR = 0.9997;95%CI,0.9996-0.9999; P = 0.0117) as CD8+NKT cells. Intercepts from Egger showed no pleiotropy and confounding factors. Furthermore, insufficient evidence was found to support the existence of heterogeneity by Cochran's Q test.

CONCLUSION

MR analysis suggested that low CD8+NKT cells and CD16-CD56 expression on NK cells were linked with a higher risk of HCC.

Abnormality in the NK-cell population is prolonged in severe COVID-19 patients

BACKGROUND

Our understanding of adaptive immune responses in patients with coronavirus disease 2019 (COVID-19) is rapidly evolving, but information on the innate immune responses by natural killer (NK) cells is still insufficient.

OBJECTIVE

We aimed to examine the phenotypic and functional status of NK cells and their changes during the course of mild and severe COVID-19.

METHODS

We performed RNA sequencing and flow cytometric analysis of NK cells from patients with mild and severe COVID-19 at multiple time points in the course of the disease using cryopreserved PBMCs.

RESULTS

In RNA-sequencing analysis, the NK cells exhibited distinctive features compared with healthy donors, with significant enrichment of proinflammatory cytokine-mediated signaling pathways. Intriguingly, we found that the unconventional CD56dimCD16neg NK-cell population expanded in cryopreserved PBMCs from patients with COVID-19 regardless of disease severity, accompanied by decreased NK-cell cytotoxicity. The NK-cell population was rapidly normalized alongside the disappearance of unconventional CD56dimCD16neg NK cells and the recovery of NK-cell cytotoxicity in patients with mild COVID-19, but this occurred slowly in patients with severe COVID-19.

CONCLUSIONS

The current longitudinal study provides a deep understanding of the NK-cell biology in COVID-19.

Antibody-Dependent Cell-mediated Cytotoxicity (ADCC) in Familial Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

BACKGROUND

Chronic fatigue syndrome (CFS) is an illness of unknown origin that may have familial risks. Low natural killer (NK) lymphocyte activity was proposed as a risk for familial CFS in 1998. Since then, there have been many studies of NK lymphocytes in CFS in general populations but few in familial CFS. Antibody-dependent cell-mediated cytotoxicity (ADCC) by NK lymphocytes helps control viral infections. ADCC is affected by variant CD16A receptors for antibody that are genetically encoded by FCGR3A.

METHODS

This report characterizes ADCC effector NK cell numbers, ADCC activities, and FCGR3A variants of five families each with 2-5 CFS patients, their family members without CFS and unrelated controls. The patients met the Fukuda diagnostic criteria. We determined: CD16Apositive blood NK cell counts; EC50s for NK cell recognition of antibody; ADCC lytic capacity; FCGR3A alleles encoding CD16A variants, ROC tests for biomarkers, and synergistic risks.

RESULTS

CFS patients and their family members had fewer CD16Apositive NK cells, required more antibody, and had ADCC that was lower than the unrelated controls. CFS family members were predominantly genetically CD16A F/F s for the variant with low affinity for antibodies. ROC tests indicated unsuitability of ADCC as a biomarker for CFS because of the low ADCC of family members without CFS. Familial synergistic risk vs. controls was evident for the combination of CD16Apositive NK cell counts with ADCC capacity.

CONCLUSIONS

low ADCC may be a risk factor for familial CFS. Furthermore, characterization of familial CFS represents an opportunity to identify pathogenic mechanisms of CFS.

Immune evasion via PD-1/PD-L1 on NK cells and monocyte/macrophages is more prominent in Hodgkin lymphoma than DLBCL

Much focus has been on the interaction of programmed cell death ligand 1 (PD-L1) on malignant B cells with programmed cell death 1 (PD-1) on effector T cells in inhibiting antilymphoma immunity. We sought to establish the contribution of natural killer (NK) cells and inhibitory CD163+ monocytes/macrophages in Hodgkin lymphoma (cHL) and diffuse large B-cell lymphoma (DLBCL). Levels of PD-1 on NK cells were elevated in cHL relative to DLBCL. Notably, CD3-CD56hiCD16-ve NK cells had substantially higher PD-1 expression relative to CD3-CD56dimCD16+ cells and were expanded in blood and tissue, more marked in patients with cHL than patients with DLBCL. There was also a raised population of PD-L1-expressing CD163+ monocytes that was more marked in patients with cHL compared with patients with DLBCL. The phenotype of NK cells and monocytes reverted back to normal once therapy (ABVD [doxorubicin 25 mg/m2, bleomycin 10 000 IU/m2, vinblastine 6 mg/m2, dacarbazine 375 mg/m2, all given days 1 and 15, repeated every 28 days] or R-CHOP [rituximab 375 mg/m2, cyclophosphamide 750 mg/m2 IV, doxorubicin 50 mg/m2 IV, vincristine 1.4 mg/m2 (2 mg maximum) IV, prednisone 100 mg/day by mouth days 1-5, pegfilgrastim 6 mg subcutaneously day 4, on a 14-day cycle]) had commenced. Tumor-associated macrophages (TAMs) expressed high levels of PD-L1/PD-L2 within diseased lymph nodes. Consistent with this, CD163/PD-L1/PD-L2 gene expression was also elevated in cHL relative to DLBCL tissues. An in vitro functional model of TAM-like monocytes suppressed activation of PD-1hi NK cells, which was reversed by PD-1 blockade. In line with these findings, depletion of circulating monocytes from the blood of pretherapy patients with cHL and patients with DLBCL enhanced CD3-CD56hiCD16-ve NK-cell activation. We describe a hitherto unrecognized immune evasion strategy mediated via skewing toward an exhausted PD-1-enriched CD3-CD56hiCD16-ve NK-cell phenotype. In addition to direct inhibition of NK cells by the malignant B cell, suppression of NK cells can occur indirectly by PD-L1/PD-L2-expressing TAMs. The mechanism is more prominent in cHL than DLBCL, which may contribute to the clinical sensitivity of cHL to PD-1 blockade.

Expression Profile of Human Fc Receptors in Mucosal Tissue: Implications for Antibody-Dependent Cellular Effector Functions Targeting HIV-1 Transmission

The majority of new Human Immunodeficiency Virus (HIV)-1 infections are acquired via sexual transmission at mucosal surfaces. Partial efficacy (31.2%) of the Thai RV144 HIV-1 vaccine trial has been correlated with Antibody-dependent Cellular Cytotoxicity (ADCC) mediated by non-neutralizing antibodies targeting the V1V2 region of the HIV-1 envelope. This has led to speculation that ADCC and other antibody-dependent cellular effector functions might provide an important defense against mucosal acquisition of HIV-1 infection. However, the ability of antibody-dependent cellular effector mechanisms to impact on early mucosal transmission events will depend on a variety of parameters including effector cell type, frequency, the class of Fc-Receptor (FcR) expressed, the number of FcR per cell and the glycoslyation pattern of the induced antibodies. In this study, we characterize and compare the frequency and phenotype of IgG (CD16 [FcγRIII], CD32 [FcγRII] and CD64 [FcγRI]) and IgA (CD89 [FcαR]) receptor expression on effector cells within male and female genital mucosal tissue, colorectal tissue and red blood cell-lysed whole blood. The frequency of FcR expression on CD14+ monocytic cells, myeloid dendritic cells and natural killer cells were similar across the three mucosal tissue compartments, but significantly lower when compared to the FcR expression profile of effector cells isolated from whole blood, with many cells negative for all FcRs. Of the three tissues tested, penile tissue had the highest percentage of FcR positive effector cells. Immunofluorescent staining was used to determine the location of CD14+, CD11c+ and CD56+ cells within the three mucosal tissues. We show that the majority of effector cells across the different mucosal locations reside within the subepithelial lamina propria. The potential implication of the observed FcR expression patterns on the effectiveness of FcR-dependent cellular effector functions to impact on the initial events in mucosal transmission and dissemination warrants further mechanistic studies.

Natural killer cells and single nucleotide polymorphisms of specific ion channels and receptor genes in myalgic encephalomyelitis/chronic fatigue syndrome

AIM

The aim of this paper was to determine natural killer (NK) cytotoxic activity and if single nucleotide polymorphisms (SNPs) and genotypes in transient receptor potential (TRP) ion channels and acetylcholine receptors (AChRs) were present in isolated NK cells from previously identified myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) patients.

SUBJECTS AND METHODS

A total of 39 ME/CFS patients (51.69±2 years old) and 30 unfatigued controls (47.60±2.39 years old) were included in this study. Patients were defined according to the 1994 Centers for Disease Control and Prevention criteria. Flow cytometry protocols were used to examine NK cytotoxic activity. A total of 678 SNPs from isolated NK cells were examined for 21 mammalian TRP ion channel genes and for nine mammalian AChR genes via the Agena Bioscience iPlex Gold assay. SNP association and genotype was determined using analysis of variance and Plink software.

RESULTS

ME/CFS patients had a significant reduction in NK percentage lysis of target cells (17%±4.68%) compared with the unfatigued control group (31%±6.78%). Of the 678 SNPs examined, eleven SNPs for TRP ion channel genes (TRPC4, TRPC2, TRPM3, and TRPM8) were identified in the ME/CFS group. Five of these SNPs were associated with TRPM3, while the remainder were associated with TRPM8, TRPC2, and TRPC4 (P<0.05). Fourteen SNPs were associated with nicotinic and muscarinic AChR genes: six with CHRNA3, while the remainder were associated with CHRNA2, CHRNB4, CHRNA5, and CHRNE (P<0.05). There were sixteen genotypes identified from SNPs in TRP ion channels and AChRs for TRPM3 (n=5), TRPM8 (n=2), TRPC4 (n=3), TRPC2 (n=1), CHRNE (n=1), CHRNA2 (n=2), CHRNA3 (n=1), and CHRNB4 (n=1) (P<0.05).

CONCLUSION

We identified a number of SNPs and genotypes for TRP ion channels and AChRs from isolated NK cells in patients with ME/CFS, suggesting these SNPs and genotypes may be involved in changes in NK cell function and the development of ME/CFS pathology. These anomalies suggest a role for dysregulation of Ca(2+) in AChR and TRP ion channel signaling in the pathomechanism of ME/CFS.

Terminal Differentiation of CD56(dim)CD16(+) Natural Killer Cells Is Associated with Increase in Natural Killer Cell Frequencies After Antiretroviral Treatment in HIV-1 Infection

HIV-1 infection results in immunological abnormalities of natural killer (NK) cells such as disturbed distribution of NK cell subsets and downmodulation of activating and upregulation of inhibitory receptors thereby diminishing NK cell killing capacity and cytokine secretion. Antiretroviral treatment (ART) is known to restore phenotype and functions of NK cells. However, the effects of ART on NK cell terminal differentiation, activation, and disturbed distribution have not been studied yet longitudinally. Here, we analyzed the effects of ART on these parameters of peripheral blood NK cells in a longitudinal as well as in a cross-sectional study. We observed that expanded CD56(-)CD16(+) NK cell frequency is inversely correlated with the frequency of CD56(dim)CD16(+) NK cells in treatment-naive HIV-1 patients. Loss of CD56(dim)CD16(+) and expansion of CD56(-)CD16(+) NK cells again restore to the levels of healthy controls after ART. Enhanced immune activation of different NK cell subsets is partially restored after ART. Terminal differentiation of CD56(dim)CD16(+) NK cells is enhanced after ART as measured by CD57 expression. Frequencies of CD57(+)CD56(dim)CD16(+) NK cells are directly correlated with the frequencies of total NK cells suggesting that an increase in the frequencies of CD57(+)CD56(dim)CD16(+) NK cells is reflected by increased frequencies of total NK cells after ART. Taken together these data demonstrate that ART has an effect on the immune restoration of NK cells and is enhanced in the terminal differentiation of CD56(dim)CD16(+) NK cells, which is associated with increased frequencies of total NK cells after ART.

Chemokine Receptor Expression on Normal Blood CD56(+) NK-Cells Elucidates Cell Partners That Comigrate during the Innate and Adaptive Immune Responses and Identifies a Transitional NK-Cell Population

Studies of chemokine receptors (CKR) in natural killer- (NK-) cells have already been published, but only a few gave detailed information on its differential expression on blood NK-cell subsets. We report on the expression of the inflammatory and homeostatic CKR on normal blood CD56(+low) CD16(+) and CD56(+high)  CD16(-/+low) NK-cells. Conventional CD56(+low) and CD56(+high) NK-cells present in the normal PB do express CKR for inflammatory cytokines, although with different patterns CD56(+low) NK-cells are mainly CXCR1/CXCR2(+) and CXCR3/CCR5(-/+), whereas mostly CD56(+high) NK-cells are CXCR1/CXCR2(-) and CXCR3/CCR5(+). Both NK-cell subsets have variable CXCR4 expression and are CCR4(-) and CCR6(-). The CKR repertoire of the CD56(+low) NK-cells approaches to that of neutrophils, whereas the CKR repertoire of the CD56(+high) NK-cells mimics that of Th1(+) T cells, suggesting that these cells are prepared to migrate into inflamed tissues at different phases of the immune response. In addition, we describe a subpopulation of NK-cells with intermediate levels of CD56 expression, which we named CD56(+int) NK-cells. These NK-cells are CXCR3/CCR5(+), they have intermediate levels of expression of CD16, CD62L, CD94, and CD122, and they are CD57(-) and CD158a(-). In view of their phenotypic features, we hypothesize that they correspond to a transitional stage, between the well-known CD56(+high) and CD56(+low) NK-cells populations.

High frequencies of polyfunctional CD8+ NK cells in chronic HIV-1 infection are associated with slower disease progression

Natural killer (NK) cells are effector and regulatory innate immune cells and play a critical role in the first line of defense against various viral infections. Although previous reports have indicated the vital contributions of NK cells to HIV-1 immune control, nongenetic NK cell parameters directly associated with slower disease progression have not been defined yet. In a longitudinal, retrospective study of 117 untreated HIV-infected subjects, we show that higher frequencies as well as the absolute numbers of CD8(+) CD3(-) lymphocytes are linked to delayed HIV-1 disease progression. We show that the majority of these cells are well-described blood NK cells. In a subsequent cross-sectional study, we demonstrate a significant loss of CD8(+) NK cells in untreated HIV-infected individuals, which correlated with HIV loads and inversely correlated with CD4(+) T cell counts. CD8(+) NK cells had modestly higher frequencies of CD57-expressing cells than CD8(-) cells, but CD8(+) and CD8(-) NK cells showed no differences in the expression of a number of activating and inhibiting NK cell receptors. However, CD8(+) NK cells exhibited a more functional profile, as detected by cytokine production and degranulation.

IMPORTANCE

We demonstrate that the frequency of highly functional CD8(+) NK cells is inversely associated with HIV-related disease markers and linked with delayed disease progression. These results thus indicate that CD8(+) NK cells represent a novel NK cell-derived, innate immune correlate with an improved clinical outcome in HIV infection.

CD3(-)CD16(-)CD56(bright) immunoregulatory NK cells are increased in the tumor microenvironment and inversely correlate with advanced stages in patients with papillary thyroid cancer

BACKGROUND

The innate immune system is the first line of defense and plays a key role in thyroid cancer development. The role of the tumor-infiltrating natural killer (NK) cells is becoming increasingly important in research and potential cancer therapies. NK cell subpopulations, CD3(-)CD16(+)CD56(dim) and CD3(-)CD16(-)CD56(bright), demonstrate a significant role in the tumor immuno-surveillance process.

METHODS

We investigated the distribution of CD3(-)CD16(+)CD56(dim) and CD3(-)CD16(-)CD56(bright) NK subpopulations in tissue and blood samples from patients with papillary thyroid cancer (PTC) and nodular goiter (NG). Twenty-eight patients with PTC, 13 patients with NG, and 50 healthy donors were included in the study. Tissue and blood samples from all patients and blood samples from healthy donors were analyzed for CD3(-)CD16(+)CD56(dim) and CD3(-)CD16(-)CD56(bright) NK cells by flow cytometry.

RESULTS

A significant predominance of CD3(-)CD16(+)CD56(dim) cells compared to CD3(-)CD16(-)CD56(bright) NK cells was found in blood samples in all groups (p<0.0001 in PTC, NG, and healthy donors). Increased infiltration by CD3(-)CD16(-)CD56(bright) NK cells was observed in thyroid tissue of patients with PTC, as compared to CD3(-)CD16(+)CD56(dim) NK cells (p=0.046), while CD3(-)CD16(+)CD56(dim) NK cells demonstrated a higher infiltration of NG tissues. CD3(-)CD16(+)CD56(dim) NK cell tissue infiltration positively correlated with advanced stages of PTC. In contrast, the CD3(-)CD16(-)CD56(bright) NK cell population was negatively associated with tumor stage in patients with PTC.

CONCLUSION

CD3(-)CD16(-)CD56(bright) NK cell infiltration seems to be associated with PTC progression. These findings contribute to a better understanding of the immune response in PTC and may lead to novel immunotherapeutic approaches in these patients.

Natural killer cells in female infertility and recurrent miscarriage: a systematic review and meta-analysis

INTRODUCTION Embryo implantation is a complex process involving maternal hormonal changes, immune responses and maturational events in the embryo. A pregnancy could fail when these events are not synchronized. It is speculated that in women, an elevation of natural killer (NK) cells may have an effect on reproductive performance, and NK cell levels in blood are currently being used as a diagnostic test to guide the initiation of therapies in patients with infertility. METHODS We conducted a systematic review to evaluate the (i) levels of NK cells in blood and endometrium in infertile versus fertile women, (ii) association between NK cells and IVF outcome, (iii) levels of NK cells in blood and endometrium in women with recurrent miscarriage (RM) versus controls. The following electronic databases were searched: Medline, EMBASE, Cochrane Library, Web of Science and National Research Register. RESULTS A total of 22 studies were included. Meta-analysis of studies that evaluated peripheral and uterine NK (uNK) cell percentages in infertile versus fertile women showed no significant difference between the two groups [standardized mean difference (SMD) -0.33; 95% confidence intervals (CI) -1.06, 0.4; P = 0.37; SMD -1.82; 95% CI -4.80, 1.17; P = 0.23 respectively]. Pooling of studies that reported peripheral NK cells as numbers showed significantly higher NK cell numbers in infertile women compared with fertile controls (SMD 3.16; 95% CI 1.07, 5.24; P = 0.003). Meta-analysis of studies that evaluated the role of NK cells in IVF outcome showed no significant difference in live birth rates in women with elevated NK cells or NK cell activity compared with women without elevated peripheral NK cells or NK cell activity (NK activity assessed using a cytotoxicity assay) (relative risk 0.57; 95% CI 0.06, 5.22; P = 0.62). Meta-analysis of studies that evaluated peripheral NK cell percentages in women with RM versus controls showed significantly higher NK cell percentages in women with RM (SMD 1.36; 95% CI 0.04, 2.69; P = 0.04). Meta-analysis of studies that evaluated peripheral NK cell numbers showed significantly higher NK cell numbers in women with RM compared with controls (SMD 0.81; 95% CI 0.47, 1.16; P < 0.00001). Meta-analysis of studies that evaluated uNK cells showed no significant difference in women with RM compared with controls (SMD 0.40; 95% CI -1.24, 2.04; P = 0.63). CONCLUSIONS Further research is needed before NK cell assessment can be recommended as a diagnostic tool in the context of female infertility or RM. There is no clear explanation as to why the results differ when data for NK cells are expressed as numbers or a percentage. On the basis of current evidence, NK cell analysis and immune therapy should be offered only in the context of clinical research.

[CD56/CD16 Expression on Mononuclear Cells and Concentration of Serum TNF-alpha in Recurrent Spontaneous Abortion.]

BACKGROUND

Recurrent spontaneous abortion (RSA) is defined as the occurrence of three or more consecutive spontaneous abortion before 20 gestational weeks. But, 40-50% of RSA still remain "unex-plained". Cytokines seem to play a critical role in the pathogenesis of unexplained RSA, and Th1 cytokines have been shown to exert deleterious effects on pregnancy. NK cytotoxicity has been reported to be predictive of subsequent abortion in women who had unexplained recurrent abortions. The aim of this study was to investigate immunophenotypic characteristics of peripheral blood mononu-clear cells and evaluate Th1 cytokine (TNF-alpha) production in women with RSA.

METHODS

The study group comprised 93 women with RSA, and the control group consisted of 40 healthy pregnant women. The population of CD56/CD16 cells was observed by using a two-color scattergram in FACScan (Becton Dickinson, San Jose CA, USA). Concentration of TNF-alpha was measured by an enzyme-linked immunoabsorbant assay (ELISA) using commercial kits (NEOGEN corporation, Lexington KY, USA).

RESULTS

The percentage of CD56+/CD16-cells were significantly higher (P<0.05) in the patients with RSA (13.40+/-7.95%) than in the pregnant control group (9.12+/-3.93%). We observed a significantly higher level of TNF-alpha (medians: 85.59+/-8.29 pg/mL versus 44.80+/-9.78 pg/mL; P<0.05) in RSA women compared to controls.

CONCLUSIONS

This study indicates that an increased proportion of CD56+/CD16-mononuclear cells and increased level of serum TNF-alpha are related to RSA. Thus, the two factors could be used as an indicator of subsequent successful implantation and maintenance of gestation.

Post-ovulatory rise of endometrial CD16(-) natural killer cells: in situ proliferation of residual cells or selective recruitment from circulating peripheral blood?

In the human endometrium, unique endometrial CD16(-) NK cells acutely increase in number after ovulation. Endometrial CD16(-) NK cells are thought to play a role in uterus-specific events, such as pregnancy or menstruation, because these NK cells are a minor leukocyte subset in circulating peripheral blood and other organs. The mechanism underlying the post-ovulatory rise of endometrial CD16(-) NK cells is largely unknown. By analogy with other organ systems, two potential mechanisms are proposed: one is in situ proliferation of residual cells and the other is selective recruitment from circulating peripheral blood. Our recent studies focus on the expression and function of potential molecules (including cytokines, chemokines and adhesion molecules) involved in these mechanisms in the human endometrium, and the regulation of these molecules by ovarian steroids. Based upon our findings, we discuss the possibility and relevance of these two potential mechanisms.

Induction of CD16+ CD56bright NK cells with antitumour cytotoxicity not only from CD16- CD56bright NK Cells but also from CD16- CD56dim NK cells

The aim of this study was to examine the effect of cytokines on different subsets of NK cells, while especially focusing on CD16(-) CD56(dim) cells and CD16(-) CD56(bright) cells. When human peripheral blood mononuclear cells (PBMC) were cultured with a combination of IL-2, IL-12 and IL-15 for several days, a minor population of CD56(bright) NK cells expanded up to 15%, and also showed potent cytotoxicities against various cancer cells. Sorting experiments revealed that unconventional CD16(-) CD56(+) NK cells (CD16(-) CD56(dim) NK cells and CD16(-) CD56(bright) NK cells, both of which are less than 1% in PBMC) much more vigorously proliferated after cytokine stimulation, whereas predominant CD16(+) CD56(dim) NK cells proliferated poorly. In addition, many of the resting CD16(-) CD56(bright) NK cells developed into CD16(+) CD56(bright) NK cells, and CD16(-) CD56(dim) NK cells developed into CD16(-) CD56(bright) NK cells and also further into CD16(+) CD56(bright) NK cells by the cytokines. CSFE label experiments further substantiated the proliferation capacity of each subset and the developmental process of CD16(+) CD56(bright) NK cells. Both CD16(-) CD56(dim) NK cells and CD16(-) CD56(bright) NK cells produced large amounts of IFN-gamma and Fas-ligands. The CD16(+) CD56(bright) NK cells showed strong cytotoxicities against not only MHC class I (-) but also MHC class I (+) tumours regardless of their expression of CD94/NKG2A presumably because they expressed NKG2D as well as natural cytotoxicity receptors. The proliferation of CD16(+) CD56(bright) NK cells was also induced when PBMC were stimulated with penicillin-treated Streptococcus pyogenes, thus suggesting their role in tumour immunity and bacterial infections.

CD56dimCD16neg cells are responsible for natural cytotoxicity against tumor targets

The activation of natural killer (NK) cells leads to degranulation and secretion of cytotoxic granula. During this process, the lytic granule membrane protein CD107a becomes detectable at the cell surface. Based on this phenomenon, we have analyzed by a novel flow cytometry-based assay, the number and phenotype of NK cells responding to tumor targets. Using human leukemia and lymphoma cell lines, we observed a close correlation between CD107a surface expression and target cell lysis, indicating that NK cell cytotoxicity can be assessed by this method. The number of degranulating NK cells was closely related to the ratio of effector and target cells and showed a maximum at a ratio of 1:1. Moreover, we were able to show that the population of CD56(dim)/CD16(neg) NK cells is primarily responsible for the cytotoxic activity against tumor targets whereas neither CD56(dim)/CD16(pos) nor CD56(bright) NK cells degranulated in response to the cell lines. Our results indicate that the CD107a assay represents a promising new method for the quantification and characterization of cells exhibiting natural cytotoxicity.

Expression of macrophage inflammatory protein-3β in human endometrium throughout the menstrual cycle

OBJECTIVE

To determine the expression of macrophage inhibitory protein-3beta (MIP-3beta), a potential chemoattractant for endometrial natural killer (NK) cells, in the human endometrium.

DESIGN

An experimental study.

SETTING

University department of obstetrics and gynecology.

PATIENT(S)

Thirty-seven fertile women with regular menstrual cycles and nonpathological endometrium, undergoing hysterectomy.

INTERVENTION(S)

Endometrium was obtained from operative samples.

MAIN OUTCOME MEASURE(S)

Paraffin-embedded endometrium was immunostained to determine the localization of MIP-3beta. The number of NK cells was counted in 10 nonoverlapping stromal areas. The MIP-3beta concentration in the homogenized endometrium was determined by ELISA.

RESULT(S)

Immunoreactivity for MIP-3beta was observed in the surface epithelia, glandular epithelia, and stroma with some menstrual cycle-dependent fluctuation. The MIP-3beta concentration was significantly higher in the late secretory phase than in the other phases. It showed a trend toward correlation with the number of endometrial NK cells.

CONCLUSION(S)

MIP-3beta was expressed in the human endometrium, but our results could not strongly support the hypothesis that MIP-3beta is a potential chemoattractant for endometrial NK cells.

Renal cell carcinoma-infiltrating natural killer cells express differential repertoires of activating and inhibitory receptors and are inhibited by specific HLA class I allotypes

Among tumor-infiltrating lymphocytes (TILs) directly isolated from renal cell carcinomas (RCCs), we found substantial numbers of natural killer (NK) cells in most tumor tissues. They could be identified reliably in situ with an antibody directed against the activating receptor (AR) NKp46 that is exclusively expressed by all NK cells. NK-enriched TILs (NK-TILs) showed cytotoxicity against major histocompatibility complex (MHC) class I-negative cell lines. The ability to detect lysis of target cells was dependent on the percentage of NK cells within the TILs, and cytotoxicity was only observed after overnight activation with low-dose interleukin-2 (IL-2). Infiltrating NK cells were found to express various inhibitory receptors (IRs); among these the CD94/NKG2A receptor complex was overrepresented compared to the autologous peripheral blood mononuclear cell (PBMC) population. Other IRs were underrepresented, indicating that NK subpopulations vary in their tumor-infiltrating capacity. IRs expressed by NK-TILs are functional since receptor engagement with MHC class I ligands presented by human leukocyte antigen (HLA)-transfected target cell lines was able to inhibit NK-mediated cytotoxicity. NK-TILs were also able to lyse autologous or allogeneic tumor cell lines in vitro. This activity correlated with low HLA class I surface expression since lysis could be inhibited by interferon (IFN)-gamma-expressing RCC transductants that displayed a higher surface density of HLA class I molecules. Therefore, NK cells infiltrating tumor tissues have an inherent ability to recognize transformed cells, but they require cytokine activation and are sensitive to inhibition by IR ligands.

Acute chylothorax in children: selective retention of memory T cells and natural killer cells

OBJECTIVE

To assess for immunodeficiency in patients with hypogammaglobulinemia in the setting of draining acute chylothorax.

STUDY DESIGN

Humoral and cellular immunity was evaluated in 8 patients with chylothorax. Chylous fluid was also analyzed to document cellular losses. Data regarding clinical course and immunologic characteristics were reviewed retrospectively.

RESULTS

All patients had hypogammaglobulinemia (IgG=179+/-35 mg/dL) as well as lymphopenia (985+/-636 cells/mm(3)). T cells were decreased and natural killer cells increased in peripheral blood. The converse was found in chylous fluid. The ratio of CD3+/CD45RA+ naive: CD3+/CD45RO+ memory T cells was greater in chyle than in peripheral blood. In vitro proliferative responses to antigens and mitogens were similar to control subjects, and previously immunized patients maintained evidence of protective vaccine-specific humoral immunity. To treat hypogammaglobulinemia, patients received intravenous immunoglobulin (IVIG) to maintain IgG within normal range; 6 of 8 patients had serious infections before receiving IVIG compared with 4 of 8 patients during the period of IVIG administration.

CONCLUSION

Draining chylothorax resulted in IgG and lymphocyte depletion with preferential retention of memory T cells and natural killer cells in the circulation. Overall, protective-specific antibody levels and T cell function were maintained. IVIG administration did not lead to discernible protection from infectious complications in this small group of patients.

Immunophenotypic characterization of normal blood CD56+lo versus CD56+hi NK-cell subsets and its impact on the understanding of their tissue distribution and functional properties

In the present study we have compared the immunophenotypic characteristics of the CD56+lo and CD56+hi NK-cell subsets in a group of normal healthy adults. Our results show that CD56+hi NK-cells display greater light-scatter properties than CD56+lo NK-cells at the same time they have higher levels of CD25 and CD122 IL-2 chains, together with a higher reactivity for HLA-DR and CD45RO and lower levels of CD45RA, supporting that, as opposed to the majority of the CD56+lo population, CD56+hi NK-cells might correspond to a subset of activated circulating NK-lymphocytes. Higher expression of the CD2 and CD7 costimulatory molecules found for the CD56+hi NK-cells would support their greater ability to respond to various stimuli. In addition, CD56+hi NK-cells expressed higher levels of several adhesion molecules such as CD2, CD11c, CD44, CD56, and CD62L compared to CD56+lo NK-cells, supporting a particular ability of these cells to migrate from blood to tissues and/or a potential advantage to form conjugates with target cells. Interestingly, CD56+lo and CD56+hi NK-cells showed a different pattern of expression of killer receptors that might determine different activation requirements for each of these NK-cell subsets. For instance, absence or low levels of CD16 expression might explain the lower antibody-dependent cytotoxicity activity of CD56+hi NK-cells. On the other hand, the virtual absence of expression of the CD158a and NKB1 immunoglobulin-like and the greater reactivity for the CD94 lectin-like killer receptors on CD56+hi in comparison to CD56+lo NK-cells might determine different MHC-class I specificities for both NK-cell subsets, a possibility that deserves further studies to be confirmed.

Status of peripheral blood natural killer cells in women with recurrent spontaneous abortions and infertility of unknown aetiology

The aim of this study was to investigate the functional status and immunophenotypic characteristics of natural killer (NK) cells in women who suffer recurrent spontaneous abortions (RSA) or have infertility of unknown aetiology. Peripheral blood mononuclear cells (PBMC) were obtained from 40 study patients and 13 normal healthy multiparous controls. NK cells were identified using anti-CD56 and anti-CD16 monoclonal antibodies (mAb). The expression of CD69, CD25, CD122, CD30, CD154, CD128 and CD94 on NK cells was detected using specific mAb and analysed by flow cytometry. CD69 expression on NK cells after ED(27) human trophoblast cell line co-culture with PBMC was also investigated. A significant increase in CD69 expression on CD56(+) NK cells was demonstrated in women with RSA (P < 0.005) and infertility (P < 0.05) as compared with that of normal controls. Conversely, CD94 expression was significantly decreased in women with RSA (P < 0.005) and infertility (P < 0.05) in comparison with that of controls. Increased CD69 expression on NK cells was induced after 24 h co-culture with ED(27). In conclusion, peripheral blood NK cells of women with RSA and infertility of unknown aetiology have higher proportions of activated NK cells in vivo. Unbalanced CD69 and CD94 expression may explain the underlying pathology.

The phenotypic heterogeneity of human natural killer cells: presence of at least 48 different subsets in the peripheral blood

Peripheral blood natural killer (NK) cells are usually defined as a homogeneous cell population. However, NK cells show heterogeneous expression of a diversity of cell surface molecules, which might reflect the diversity of NK-cell functions. Therefore, a more specific phenotypic definition of NK cells is necessary. In this study, we made an inventory of phenotypic subsets that are present within the peripheral blood NK-cell population of healthy donors based on differential expression of nine cell-surface markers. Using three-colour flow cytometric analysis we were able to define at least 48 different CD56(+) NK-cell subsets within the peripheral blood. This phenotypic heterogeneity appeared to be stable among healthy individuals, and was also steady within CD56(dim) and CD56(bright) NK populations, indicating a possible role for these subsets in NK-cell function or differentiation.

Expression and coreceptor activity of STRL33/Bonzo on primary peripheral blood lymphocytes

CCR5 and CXCR4 are the major coreceptors that mediate human immunodeficiency virus 1 (HIV-1) infection, while most simian immunodeficiency virus (SIV) isolates use CCR5. A number of alternative coreceptors can also mediate infection of some virus strains in vitro, although little is known about their in vivo relevance. Therefore, we characterized the expression pattern and coreceptor activity of one of these alternative coreceptors, STRL33/Bonzo, using a newly developed monoclonal antibody. In addition to being highly expressed (approximately 1000-7000 STRL33 ABS [antibody binding sites]) on specific subsets of natural killer cells (CD3−/CD16−/low/CD56+ and CD3−/CD16low/CD56−) and CD19+ B lymphocytes (approximately 300-5000 STRL33 ABS), STRL33 was expressed at levels sufficient to support virus infection on freshly isolated, truly naive CD4+/CD45RA+/CD62L+cells (6000-11 000 ABS). STRL33 expression on peripheral blood mononuclear cells (PBMCs) was increased by mitogenic stimulation (OKT3/IL-2 [interleukin-2] had a greater effect than phytohemaglutinin (PHA)/IL-2), but it was dramatically decreased upon Ficoll purification. Infection of CCR5− human peripheral blood lymphocytes (PBLs) showed that 2 different SIV envelope (Env) proteins mediated entry into STRL33+cells. More importantly, the preferential infection of STRL33+ cells in CCR5− PBLs by an R5/X4/STRL33 HIV-1 maternal isolate in the presence of a potent CXCR4 antagonist (AMD3100) suggests that STRL33 can be used as a coreceptor by HIV-1 on primary cells. Rhesus macaque (rh) STRL33 was used less efficiently than human STRL33 by the majority of SIV Env proteins tested despite similar levels of expression, thereby making it less likely that STRL33 is a relevant coreceptor in the rhesus macaque system. In summary, the expression pattern and coreceptor activity of STRL33 suggest its involvement in trafficking of tumor-infiltrating lymphocytes and indicate that STRL33 may be a relevant coreceptor in vivo.

Expression and coreceptor activity of STRL33/Bonzo on primary peripheral blood lymphocytes

CCR5 and CXCR4 are the major coreceptors that mediate human immunodeficiency virus 1 (HIV-1) infection, while most simian immunodeficiency virus (SIV) isolates use CCR5. A number of alternative coreceptors can also mediate infection of some virus strains in vitro, although little is known about their in vivo relevance. Therefore, we characterized the expression pattern and coreceptor activity of one of these alternative coreceptors, STRL33/Bonzo, using a newly developed monoclonal antibody. In addition to being highly expressed (approximately 1000-7000 STRL33 ABS [antibody binding sites]) on specific subsets of natural killer cells (CD3−/CD16−/low/CD56+ and CD3−/CD16low/CD56−) and CD19+ B lymphocytes (approximately 300-5000 STRL33 ABS), STRL33 was expressed at levels sufficient to support virus infection on freshly isolated, truly naive CD4+/CD45RA+/CD62L+cells (6000-11 000 ABS). STRL33 expression on peripheral blood mononuclear cells (PBMCs) was increased by mitogenic stimulation (OKT3/IL-2 [interleukin-2] had a greater effect than phytohemaglutinin (PHA)/IL-2), but it was dramatically decreased upon Ficoll purification. Infection of CCR5− human peripheral blood lymphocytes (PBLs) showed that 2 different SIV envelope (Env) proteins mediated entry into STRL33+cells. More importantly, the preferential infection of STRL33+ cells in CCR5− PBLs by an R5/X4/STRL33 HIV-1 maternal isolate in the presence of a potent CXCR4 antagonist (AMD3100) suggests that STRL33 can be used as a coreceptor by HIV-1 on primary cells. Rhesus macaque (rh) STRL33 was used less efficiently than human STRL33 by the majority of SIV Env proteins tested despite similar levels of expression, thereby making it less likely that STRL33 is a relevant coreceptor in the rhesus macaque system. In summary, the expression pattern and coreceptor activity of STRL33 suggest its involvement in trafficking of tumor-infiltrating lymphocytes and indicate that STRL33 may be a relevant coreceptor in vivo.