Structure/function of human killer cell immunoglobulin-like receptors: lessons from polymorphisms, evolution, crystal structures and mutations

Class I HLA haplotypes form two schools that educate NK cells in different ways

Natural killer (NK) cells are lymphocytes having vital functions in innate and adaptive immunity, as well as placental reproduction. Controlling education and functional activity of human NK cells are various receptors that recognize HLA class I on the surface of tissue cells. Epitopes of polymorphic HLA-A,-B and -C are recognized by equally diverse killer cell immunoglobulin-like receptors (KIR). In addition, a peptide cleaved from the leader sequence of HLA-A,-B or -C must bind to HLA-E for it to become a ligand for the conserved CD94:NKG2A receptor. Methionine/threonine dimorphism at position -21 of the leader sequence divides HLA-B allotypes into a majority having -21T that do not supply HLA-E binding peptides and a minority having -21M, that do. Genetic analysis of human populations worldwide shows how haplotypes with -21M HLA-B rarely encode the KIR ligands: Bw4⁺HLA-B and C2⁺HLA-C KIR. Thus there are two fundamental forms of HLA haplotype: one preferentially supplying CD94:NKG2A ligands, the other preferentially supplying KIR ligands. -21 HLA-B dimorphism divides the human population into three groups: M/M, M/T and T/T. Mass cytometry and assays of immune function, shows how M/M and M/T individuals have CD94:NKG2A⁺ NK cells which are better educated, phenotypically more diverse and functionally more potent than those in T/T individuals. Fundamental new insights are given to genetic control of NK cell immunity and the evolution that has limited the number of NK cell receptor ligands encoded by an HLA haplotype. These finding suggest new ways to dissect the numerous clinical associations with HLA class I.

Development of Novel Immunotherapies for Multiple Myeloma

Multiple myeloma (MM) is a disorder of terminally differentiated plasma cells characterized by clonal expansion in the bone marrow (BM). It is the second-most common hematologic malignancy. Despite significant advances in therapeutic strategies, MM remains a predominantly incurable disease emphasizing the need for the development of new treatment regimens. Immunotherapy is a promising treatment modality to circumvent challenges in the management of MM. Many novel immunotherapy strategies, such as adoptive cell therapy and monoclonal antibodies, are currently under investigation in clinical trials, with some already demonstrating a positive impact on patient survival. In this review, we will summarize the current standards of care and discuss major new approaches in immunotherapy for MM.

Role of KIR and CD16A genotypes in colorectal carcinoma genetic risk and clinical stage

Background

NK cell cytotoxicity is regulated by the types of the interaction between killer immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) class I ligands on target cells and the different binding affinity of the Fcγ receptor IIIA (CD16A) for IgG-coated tumor cells. Thus, it is conceivable that KIR and CD16A gene contents may contribute to the function of NK cells by modulating an immune response in the colorectal carcinoma (CRC) microenvironment. This hypothesis is supported by recent evidence suggesting that NK cells improve the clinical course of CRC patients by enhancing the anti-CRC effect of CD8 + T cells. This information provides the rationale to test the hypothesis whether the independent KIR segregation and specificity, as well as CD16A gene polymorphisms, have an impact on CRC.

Methods

Using polymerase chain reaction-sequence-specific primers (PCR-SSP) and sequence-based typing (SBT), we investigated KIR/HLA-C complex and CD16A (48H/R/L,158V/F) gene polymorphisms in 52 CRC patients and 61 local healthy controls (LCTRs).

Results

The allele frequency (AF) of at least five activating KIR (aKIRs) of the B haplotype (p = 0.036, OR 0.204), KIR2DL2 (p = 0.047, OR 0.2616), and KIR2DS2 genes (5.8 vs LCTR 13.8 % and vs. Fasano’s CTR 16.3 %, p = 0.05, OR 0.3145), in the absence of their cognate HLA-C1 ligands, were significantly associated with a reduced genetic risk of CRC. In contrast, CD16A-48H polymorphism was positively associated with an increased genetic risk of CRC (p = 0.05, OR 2.761). The latter was also found to be correlated with advanced stages of disease [III and IV (p = 0.03, OR 3.625)].

Conclusions

Our data suggest that the analysis of aKIRs and KIR2DL2 gene and CD16A-48H may be of interest for the identification of individuals at reduced and increased genetic risk of CRC, respectively.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1001-y) contains supplementary material, which is available to authorized users.

Defining KIR and HLA Class I Genotypes at Highest Resolution via High-Throughput Sequencing

The physiological functions of natural killer (NK) cells in human immunity and reproduction depend upon diverse interactions between killer cell immunoglobulin-like receptors (KIRs) and their HLA class I ligands: HLA-A, HLA-B, and HLA-C. The genomic regions containing the KIR and HLA class I genes are unlinked, structurally complex, and highly polymorphic. They are also strongly associated with a wide spectrum of diseases, including infections, autoimmune disorders, cancers, and pregnancy disorders, as well as the efficacy of transplantation and other immunotherapies. To facilitate study of these extraordinary genes, we developed a method that captures, sequences, and analyzes the 13 KIR genes and HLA-A, HLA-B, and HLA-C from genomic DNA. We also devised a bioinformatics pipeline that attributes sequencing reads to specific KIR genes, determines copy number by read depth, and calls high-resolution genotypes for each KIR gene. We validated this method by using DNA from well-characterized cell lines, comparing it to established methods of HLA and KIR genotyping, and determining KIR genotypes from 1000 Genomes sequence data. This identified 116 previously uncharacterized KIR alleles, which were all demonstrated to be authentic by sequencing from source DNA via standard methods. Analysis of just two KIR genes showed that 22% of the 1000 Genomes individuals have a previously uncharacterized allele or a structural variant. The method we describe is suited to the large-scale analyses that are needed for characterizing human populations and defining the precise HLA and KIR factors associated with disease. The methods are applicable to other highly polymorphic genes.

The promise of immunotherapy in head and neck squamous cell carcinoma

Squamous cell cancers of the head and neck (HNSCC) comprise a diverse group of malignancies that includes tobacco-related tumors in addition to an increasing number of human papillomavirus-associated cancers. Independently of cause, there is a growing body of evidence supporting that the immune system plays a pivotal role in HNSCC development, as tumor cells evade immunosurveillance by exploiting inhibitory checkpoint pathways that suppress anti-tumor T-cell responses. HNSCC cells have the ability to manipulate the immune system through a variety of different mechanisms, forcing it to promote tumor growth and spread. Over the last decade, discoveries in immunologic research resulted in increased understanding of complex interactions between HNSCC and the host immune system as well as T-cell regulatory mechanisms, promoting the development of a variety of novel immunotherapies. Following the availability of novel immunotherapeutic strategies, the challenge for clinicians is to understand how and in which clinical setting to use these agents in order to provide greater clinical benefit for patients. Combination of immunotherapies with standard treatment approaches also represents an evolving field of research. Herein, we provide a comprehensive review of immune escape mechanisms in HNSCC, as well as current immunotherapy approaches under investigation.

Expression of PD-L1 and HLA Class I in Esophageal Squamous Cell Carcinoma: Prognostic Factors for Patient Outcome

BACKGROUND

Programmed cell death 1 ligand 1 (PD-L1) and human leukocyte antigen (HLA) class I molecules on malignant cell surfaces are pivotal for tumor immunity. The clinical significance of their expression in patients with esophageal squamous cell carcinoma (ESCC) remains to be determined.

METHODS

PD-L1 and HLA class I protein expression was investigated by immunohistochemical staining of resected specimens from 90 ESCC patients who underwent radical surgery without preoperative therapy. The relationships between the expression of PD-L1 and HLA class I and clinicopathologic factors and patient prognosis were assessed.

RESULTS

High expression of PD-L1 and HLA class I were observed in 17 (18.9 %) and 35 (38.9 %) of 90 cases, respectively. High PD-L1 expression was correlated with the depth of tumor invasion (P = 0.0379), lymph node metastasis (P = 0.0031), recurrence (P = 0.0085), and poor overall survival (OS) (5-year survival rate; low/high: 60.9/28.4 %, P = 0.0110). Among those patients with high expression of HLA class I, high PD-L1 expression was correlated with significantly poorer recurrence-free survival (median survival time, low/high: 102.5/3.1 months, P = 0.0016) and poorer OS (median survival time, low/high: 102.5/13.1 months, P = 0.0027). Multivariate analysis showed that combined high PD-L1/high HLA class I expression was an independent prognostic factor for recurrence-free survival (hazard ratio 2.88, 95 % confidence interval 1.02-7.04, P = 0.0455) and OS (hazard ratio 2.95, 95 % confidence interval 1.03-7.50, P = 0.0447).

CONCLUSIONS

High PD-L1 expression was a significant independent prognostic factor in ESCC patients with high HLA class I expression.

The emerging role of immunotherapy in head and neck squamous cell carcinoma (HNSCC): anti-tumor immunity and clinical applications

Head and neck squamous cell carcinoma (HNSCC) carries a poor prognosis, with low survival rates for advanced stage tumors and minimal improvement in survival trends through the past decades. It is becoming increasingly clear that HNSCC oncogenesis and evolution is characterized by profound immune defects, as cancer cells evade immunosurveillance due to accumulation of genetic mutations and tumor heterogeneity. Improved understanding of the role of the immune system in cancer has led to the identification of novel therapeutic targets, which are being investigated for their potential to provide durable responses. In this review, we will summarize the role of the immune system in HNSCC, the rationale behind immunotherapy strategies and their clinical applications.

Killer cell immunoglobulin-like receptor and human leukocyte antigen gene profiles in a cohort of HIV-infected Mexican Mestizos

Killer cell immunoglobulin-like receptors (KIRs) represent the most polymorphic genes responsible for natural killer cell function, while human leukocyte antigen (HLA) class I molecules define and restrict cytotoxic T lymphocyte responses. Specific KIR, HLA, or KIR-HLA combinations have been implicated in the outcome of human immunodeficiency virus (HIV) disease. The remarkable polymorphism of KIR and HLA genes warrants descriptive gene frequency studies in different populations, as well as their impact on HIV disease progression in different immunogenetic contexts. We report KIR and HLA class I gene profiles of 511 unrelated HIV-infected Mexican Mestizo individuals from 18 states for whom genetic ancestry proportions were assessed. KIR and HLA gene profiles were compared between individuals from the north and central-south regions of the country and between individuals with higher European (EUR) or Amerindian (AMI) genetic ancestry component. A total of 65 KIR genotypes were observed, 11 harboring novel KIR gene combinations. A total of 164 HLA alleles were observed: 43 HLA-A, 87 HLA-B, and 34 HLA-C. Differences in the distribution of 12 HLA alleles were observed between individuals with higher AMI or EUR ancestry components (p < 0.05, q < 0.2). After correcting for genetic ancestry, only individual HLA alleles were associated with HIV disease progression, including a novel association with A*02:06, an Amerindian HLA allele associated with lower CD4+ T cell counts. No KIR effects were significant. Our results highlight the advantages of considering a detailed genetic stratification within populations when studying genetic profiles that could be implicated in disease-association studies.

Interactions between maternal killer cell immunoglobulin receptor genes and foetal HLA ligand genes contribute to type 1 diabetes susceptibility in Han Chinese

In this study, we aimed to test the hypothesis that KIR haplotypes (that interact with HLA class I molecules) are associated with susceptibility in patients with T1DM in utero through maternal-foetal interaction of KIR and their HLA class I ligands in Han Chinese population. We determined the KIR genes and KIR/ligand gene combination frequencies in 59 Han Chinese children with T1D and their mothers and compared it with 159 healthy control children and their mothers. The absence of KIR-2DS1 in the mother and the presence of HLA-C2 ligand in the child were negatively associated with type 1 diabetes in the child. Our results indicate that maternal KIR genes and their interaction with foetal HLA-C2 may contribute to the risk of type 1 diabetes among Han Chinese children.

Chicken TREM-B1, an Inhibitory Ig-Like Receptor Expressed on Chicken Thrombocytes

Triggering receptors expressed on myeloid cells (TREM) form a multigene family of immunoregulatory Ig-like receptors and play important roles in the regulation of innate and adaptive immunity. In chickens, three members of the TREM family have been identified on chromosome 26. One of them is TREM-B1 which possesses two V-set Ig-domains, an uncharged transmembrane region and a long cytoplasmic tail with one ITSM and two ITIMs indicating an inhibitory function. We generated specific monoclonal antibodies by immunizing a Balb/c mouse with a TREM-B1-FLAG transfected BWZ.36 cell line and tested the hybridoma supernatants on TREM-B1-FLAG transfected 2D8 cells. We obtained two different antibodies specific for TREM-B1, mab 7E8 (mouse IgG1) and mab 1E9 (mouse IgG2a) which were used for cell surface staining. Single and double staining of different tissues, including whole blood preparations, revealed expression on thrombocytes. Next we investigated the biochemical properties of TREM-B1 by using the specific mab 1E9 for immunoprecipitation of either lysates of surface biotinylated peripheral blood cells or stably transfected 2D8 cells. Staining with streptavidin coupled horse radish peroxidase revealed a glycosylated monomeric protein of about 50 kDa. Furthermore we used the stably transfected 2D8 cell line for analyzing the cytoplasmic tyrosine based signaling motifs. After pervanadate treatment, we detected phosphorylation of the tyrosine residues and subsequent recruitment of the tyrosine specific protein phosphatase SHP-2, indicating an inhibitory potential for TREM-B1. We also showed the inhibitory effect of TREM-B1 in chicken thrombocytes using a CD107 degranulation assay. Crosslinking of TREM-B1 on activated primary thrombocytes resulted in decreased CD107 surface expression of about 50-70%.

Description of the novel KIR2DL4*035 allele identified using high-throughput sequencing

A newly identified allele of the KIR2DL4 natural killer cell receptor for human leukocyte antigen (HLA) class I.

Killer immunoglobulin receptor genes and their HLA-C ligand are associated with Type 1 diabetes in an Eastern Indian population

AIM

Killer immunoglobulin-like receptors (KIRs) and their interaction with HLA class I ligands have been shown to be associated with Type 1 diabetes mellitus. The aim of our study was to investigate the influence of KIR genes and their HLA-C ligands for susceptibility to Type 1 diabetes in patients from Eastern India.

METHODS

A total of 135 patients with Type 1 diabetes and 98 healthy subjects from Eastern India were typed for KIR genes and HLA-C ligands using PCR-based genotyping. The frequencies of these genes were compared between patients and controls.

RESULTS

Comparison of KIR genes between Type 1 diabetes patients and healthy subjects revealed significantly different frequencies of KIRs 2DL2 and 2DS4. The presence of HLA-C1 was negatively associated with disease. The presence of both HLA-C1 and -C2 showed a negative association with Type 1 diabetes, whereas the absence of C1 and presence of C2 was positively associated with disease. Stratification analysis of HLA-C ligands and KIRs showed significant associations between Type 1 diabetes and 2DL2+/C1-, 2DL2-/C1+, 2DL3+/C1+, 2DL3+/C1- and 2DS2+/C1-.

CONCLUSIONS

Our results suggest that the interaction of KIRs with HLA-C ligands are significant and certain combinations contribute to susceptibility to and protection against Type 1 diabetes.

NK cells and cancer: you can teach innate cells new tricks

Natural killer (NK) cells are the prototype innate lymphoid cells endowed with potent cytolytic function that provide host defence against microbial infection and tumours. Here, we review evidence for the role of NK cells in immune surveillance against cancer and highlight new therapeutic approaches for targeting NK cells in the treatment of cancer.

Differential loss of natural killer cell activity in patients with acute myocardial infarction and stable angina pectoris

BACKGROUND

To evaluate the activity of natural killer cells through their inhibitory and activating receptors and quantity in peripheral blood mononuclear cells extracted from patients with acute myocardial infarction, stable angina pectoris and the controls.

METHODS

100 patients with myocardial infarction, 100 with stable angina, and 20 healthy volunteers were recruited into the study. 20 randomly chosen people per group were examined for the whole human genome microarray analysis to detect the gene expressions of all 40 inhibitory and activating natural killer cell receptors. Flow cytometry analysis was applied to all 200 patients to measure the quantity of natural killer cells.

RESULTS

In myocardial infarction group, the mRNA expressions of six inhibitory receptors KIR2DL2, KIR3DL3, CD94, NKG2A, KLRB1, KLRG1, and eight activating receptors KIR2DS3, KIR2DS5, NKp30, NTB-A, CRACC, CD2, CD7 and CD96 were significantly down-regulated (P<0.05) compared with both angina patients and the controls. There was no statistical difference in receptor expressions between angina patients and control group. The quantity of natural killer cells was significantly decreased in both infarction and angina patients compared with normal range (P<0.001).

CONCLUSIONS

The significant mRNAs down-regulation of several receptors in myocardial infarction group and reduction in the quantity of natural killer cells in both myocardial infarction and angina patients showed a quantitative loss and dysfunction of natural killer cells in myocardial infarction patients.

In-vitro activation of natural killer cells from regional lymph nodes of melanoma patients with interleukin-2 and interleukin-15

Regional lymph nodes (LNs) represent the first barrier in lymphogenic tumor dissemination in melanoma. Natural killer (NK) cells, the effector cell subpopulation of the innate immune system, are in the first line of antitumor immune defense. Therefore, the aim of this study was to investigate the effect of interleukin (IL)-2 and IL-15, two cytokines with similar immune-enhancing effects, on antitumor cytotoxic function and immunophenotype of NK cells from regional LNs of melanoma patients. Mononuclear cells purified from regional LNs of 50 melanoma patients in clinical stage II-IV were treated in vitro for 72 h and 7 days with 200 IU/ml rhIL-2 and 25 ng/ml IL-15 at 37°C in 5% CO2. Both cytokines significantly augmented NK cell cytotoxic activity, transcription of the cytotoxic molecule perforin, and the level of functionally mature perforin in both nonmetastatic and metastatic regional LNs. IL-2 treatment increased the percentage of CD3CD56 NK cells by increasing the CD56 NK cell subset in both nonmetastatic and metastatic LNs, whereas IL-15 treatment did not affect the percentage of NK cells and their subsets. Both cytokines increased on NK cells from nonmetastatic and metastatic LNs the expression of CD69 early activation antigen, the NKG2D activating receptor, as well as CD16 and inhibitory killer-cell immunoglobulin-like receptor CD158b, both inherent to the mature and the cytotoxic NK cell phenotype. In conclusion, our data may indicate the therapeutic potential of the NK cell population from regional LNs either as immunotherapeutic targets or as adoptively transferred after activation with IL-2 or IL-15.

Negative regulation of natural killer cell in tumor tissue and peripheral blood of oral squamous cell carcinoma

Natural killer (NK) cells are the key lymphocytes in solid tumors. Its activity is regulated by both germline encoded receptors and cytokine microenvironment. We conducted a case-control study to investigate the activation status of NK cell in oral squamous cell carcinoma (OSCC). NK cell activation was assessed in context of NK cell cytotoxicity and transcript expression of NK cell receptors (NKp46 and KIRs) and NK cell associated cytokines (IL-1β, IL-2, IL-10, IL-12β, IL-15, IL-18, IL-21, IFN-γ, TNF-α and TGF-β). The results revealed possible mechanisms involved in reduced NK cell activation in peripheral circulation: quantitative deficiency of NK cell number and lowered cytotoxicity together with qualitative NK impairments caused by--(1) decreased expression of NK activating receptor NKp46, (2) increased expression of NK suppressive cytokines--IL-10 and TGF-β and (3) induction of FOXP3(+)CTLA4(+) suppressor cells. On the other hand, in the tumor tissue, escape of NK immune surveillance appeared to be modulated by upregulation of TGF-β and IL-10 together with downregulation of NK cell activating cytokines (IL-2, IL-12β, IL-15, IL-18, IL-21 and IFN-γ) and NK receptors (NKp46 and KIRs). In addition, our study supported the earlier contention that TNF-α and IL-1β expression levels may be used as markers of malignant transformation in oral leukoplakia. In conclusion, the study provided an insight into the negative regulation of NK cell in tumor tissue and peripheral blood of OSCC patients, which can be exploited to boost the current NK cell and cytokine based immunotherapy for the treatment of oral cancer.

Immunogenetics of type 1 diabetes: A comprehensive review

Type 1 diabetes (T1D) results from the autoimmune destruction of insulin-producing beta cells in the pancreas. Prevention of T1D will require the ability to detect and modulate the autoimmune process before the clinical onset of disease. Genetic screening is a logical first step in identification of future patients to test prevention strategies. Susceptibility to T1D includes a strong genetic component, with the strongest risk attributable to genes that encode the classical Human Leukocyte Antigens (HLA). Other genetic loci, both immune and non-immune genes, contribute to T1D risk; however, the results of decades of small and large genetic linkage and association studies show clearly that the HLA genes confer the most disease risk and protection and can be used as part of a prediction strategy for T1D. Current predictive genetic models, based on HLA and other susceptibility loci, are effective in identifying the highest-risk individuals in populations of European descent. These models generally include screening for the HLA haplotypes "DR3" and "DR4." However, genetic variation among racial and ethnic groups reduces the predictive value of current models that are based on low resolution HLA genotyping. Not all DR3 and DR4 haplotypes are high T1D risk; some versions, rare in Europeans but high frequency in other populations, are even T1D protective. More information is needed to create predictive models for non-European populations. Comparative studies among different populations are needed to complete the knowledge base for the genetics of T1D risk to enable the eventual development of screening and intervention strategies applicable to all individuals, tailored to their individual genetic background. This review summarizes the current understanding of the genetic basis of T1D susceptibility, focusing on genes of the immune system, with particular emphasis on the HLA genes.

Killer-cell immunoglobulin-like receptor and human leukocyte antigen-C genes in common variable immunodeficiency

BACKGROUND

We aimed herein to investigate the killer-cell immunoglobulin-like receptor (KIR) genes and human leukocyte antigen (HLA)-C alleles in patients with common variable immunodeficiency (CVID), and to reveal their differences from those in healthy population.

METHODS

In all, 18 patients who have been diagnosed with CVID and 15 living donors of kidney transplant recipients were enrolled in the study. Polymerase chain reaction-sequence-specific primer (PCR-SSP) typing method was used in molecular genetic analysis. The frequencies of the genes in the study groups were statistically compared with each other using chi-square or Fisher exact tests, whichever were appropriate.

RESULTS

Although there was no significant difference between both study groups with respect to distribution of KIR and HLA-C2 group genes, HLA-Cw7 allele frequency in patients with CVID was significantly lower than that in healthy population (P = 0.008).

CONCLUSION

This present study results support that HLA-Cw7 allele, an inhibitor of KIR ligand, may play a role in the pathogenesis of CVID.

MHC structure and function – antigen presentation. Part 1

The setting for the occurrence of an immune response is that of the need to cope with a vast array of different antigens from both pathogenic and non-pathogenic sources. When the first barriers against infection and innate defense fail, adaptive immune response enters the stage for recognition of the antigens by means of extremely variable molecules, namely immunoglobulins and T-cell receptors. The latter recognize the antigen exposed on cell surfaces, in the form of peptides presented by the HLA molecule. The first part of this review details the central role played by these molecules, establishing the close connection existing between their structure and their antigen presenting function.

OX40 Agonists and Combination Immunotherapy: Putting the Pedal to the Metal

Recent studies have highlighted the therapeutic efficacy of immunotherapy, a class of cancer treatments that utilize the patient’s own immune system to destroy cancerous cells. Within a tumor the presence of a family of negative regulatory molecules, collectively known as “checkpoint inhibitors,” can inhibit T cell function to suppress anti-tumor immunity. Checkpoint inhibitors, such as CTLA-4 and PD-1, attenuate T cell proliferation and cytokine production. Targeted blockade of CTLA-4 or PD-1 with antagonist monoclonal antibodies (mAbs) releases the “brakes” on T cells to boost anti-tumor immunity. Generating optimal “killer” CD8 T cell responses also requires T cell receptor activation plus co-stimulation, which can be provided through ligation of tumor necrosis factor receptor family members, including OX40 (CD134) and 4-1BB (CD137). OX40 is of particular interest as treatment with an activating (agonist) anti-OX40 mAb augments T cell differentiation and cytolytic function leading to enhanced anti-tumor immunity against a variety of tumors. When used as single agents, these drugs can induce potent clinical and immunologic responses in patients with metastatic disease. However, each of these agents only benefits a subset of patients, highlighting the critical need for more effective combinatorial therapeutic strategies. In this review, we will discuss our current understanding of the cellular and molecular mechanisms by which OX40 agonists synergize with checkpoint inhibitor blockade to augment T cell-mediated anti-tumor immunity and the potential opportunities for clinical translation of combinatorial immunotherapeutic strategies.

Innate immunity in solid organ transplantation: an update and therapeutic opportunities

Innate immunity is increasingly recognized as a major player in transplantation. In addition to its role in inflammation in the early post-transplant period, innate immunity shapes the differentiation of cells of adaptive immunity, with a capacity to promote either rejection or tolerance. Emerging data indicate that innate allorecognition, a characteristic previously limited to lymphocytes, is involved in allograft rejection. This review briefly summarizes the physiology of each component of the innate immune system in the context of transplantation and presents the current or promising therapeutic applications, such as cellular, anticomplement and anticytokine therapies.

Genetics of ANCA-associated Vasculitides

The distribution of the anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides (AAV) is not uniform across geographical regions and ethnic and racial groups, suggesting that genetic and environmental factors affect the pathogenesis of these diseases. In addition, genetic factors affect not only the clinical syndrome phenotypes and their prognosis, but also ANCA specificity; these data suggest that AAV may need reclassification. Several genes have been evaluated, including ANCA targets and those of the immune system, for example co-stimulatory molecules, signaling regulators, cytokines, Fc and other receptors, and other proteins. This article provides a review of genetic factors affecting the pathogenesis and prognosis of AAV. Further studies to determine the effect of genetic factors on the clinical syndrome phenotypes and ANCA specificity need to be performed across different ethnic groups.

NK cells with KIR2DS2 immunogenotype have a functional activation advantage to efficiently kill glioblastoma and prolong animal survival

Glioblastomas (GBMs) are lethal brain cancers that are resistant to current therapies. We investigated the cytotoxicity of human allogeneic NK cells against patient-derived GBM in vitro and in vivo, as well as mechanisms mediating their efficacy. We demonstrate that KIR2DS2 immunogenotype NK cells were more potent killers, notwithstanding the absence of inhibitory killer Ig-like receptor (KIR)-HLA ligand mismatch. FACS-sorted and enriched KIR2DS2(+) NK cell subpopulations retained significantly high levels of CD69 and CD16 when in contact with GBM cells at a 1:1 ratio and highly expressed CD107a and secreted more soluble CD137 and granzyme A. In contrast, KIR2DS2(-) immunogenotype donor NK cells were less cytotoxic against GBM and K562, and, similar to FACS-sorted or gated KIR2DS2(-) NK cells, significantly diminished CD16, CD107a, granzyme A, and CD69 when in contact with GBM cells. Furthermore, NK cell-mediated GBM killing in vitro depended upon the expression of ligands for the activating receptor NKG2D and was partially abrogated by Ab blockade. Treatment of GBM xenografts in NOD/SCID mice with NK cells from a KIR2DS2(+) donor lacking inhibitory KIR-HLA ligand mismatch significantly prolonged the median survival to 163 d compared with vehicle controls (log-rank test, p = 0.0001), in contrast to 117.5 d (log-rank test, p = 0.0005) for NK cells with several inhibitory KIR-HLA ligand mismatches but lacking KIR2DS2 genotype. Significantly more CD56(+)CD16(+) NK cells from a KIR2DS2(+) donor survived in nontumor-bearing brains 3 wk after infusion compared with KIR2DS2(-) NK cells, independent of their proliferative capacity. In conclusion, KIR2DS2 identifies potent alloreactive NK cells against GBM that are mediated by commensurate, but dominant, activating signals.

Ly49E expression on CD8αα-expressing intestinal intraepithelial lymphocytes plays no detectable role in the development and progression of experimentally induced inflammatory bowel diseases

The Ly49E NK receptor is a unique inhibitory receptor, presenting with a high degree of conservation among mouse strains and expression on both NK cells and intraepithelial-localised T cells. Amongst intraepithelial-localised T cells, the Ly49E receptor is abundantly expressed on CD8αα-expressing innate-like intestinal intraepithelial lymphocytes (iIELs), which contribute to front-line defense at the mucosal barrier. Inflammatory bowel diseases (IBDs), encompassing Crohn's disease and ulcerative colitis, have previously been suggested to have an autoreactive origin and to evolve from a dysbalance between regulatory and effector functions in the intestinal immune system. Here, we made use of Ly49E-deficient mice to characterize the role of Ly49E receptor expression on CD8αα-expressing iIELs in the development and progression of IBD. For this purpose we used the dextran sodium sulphate (DSS)- and trinitrobenzenesulfonic-acid (TNBS)-induced colitis models, and the TNFΔARE ileitis model. We show that Ly49E is expressed on a high proportion of CD8αα-positive iIELs, with higher expression in the colon as compared to the small intestine. However, Ly49E expression on small intestinal and colonic iIELs does not influence the development or progression of inflammatory bowel diseases.

The ap-2 clathrin adaptor mediates endocytosis of an inhibitory killer cell Ig-like receptor in human NK cells

Stable surface expression of human inhibitory killer cell Ig-like receptors (KIRs) is critical for controlling NK cell function and maintaining NK cell tolerance toward normal MHC class I(+) cells. Our recent experiments, however, have found that Ab-bound KIR3DL1 (3DL1) readily leaves the cell surface and undergoes endocytosis to early/recycling endosomes and subsequently to late endosomes. We found that 3DL1 internalization is at least partially mediated by an interaction between the μ2 subunit of the AP-2 clathrin adaptor complex and ITIM tyrosine residues in the cytoplasmic domain of 3DL1. Disruption of the 3DL1/μ2 interaction, either by mutation of the ITIM tyrosines in 3DL1 or mutation of μ2, significantly diminished endocytosis and increased surface expression of 3DL1 in human primary NK cells and cell lines. Furthermore, we found that the 3DL1/AP-2 interaction is diminished upon Ab engagement with the receptor, as compared with untreated cells. Thus, we have identified AP-2-mediated endocytosis as a mechanism regulating the surface levels of inhibitory KIRs through their ITIM domains. Based on our results, we propose a model in which nonengaged KIRs are internalized by this mechanism, whereas engagement with MHC class I ligand would diminish AP-2 binding, thereby prolonging stable receptor surface expression and promoting inhibitory function. Furthermore, this ITIM-mediated mechanism may similarly regulate the surface expression of other inhibitory immune receptors.

Distinct assembly profiles of HLA-B molecules

MHC class I polymorphisms are known to influence outcomes in a number of infectious diseases, cancers, and inflammatory diseases. Human MHC class I H chains are encoded by the HLA-A, HLA-B, and HLA-C genes. These genes are highly polymorphic, with the HLA-B locus being the most variable. Each HLA class I protein binds to a distinct set of peptide Ags, which are presented to CD8(+) T cells. HLA-disease associations have been shown in some cases to link to the peptide-binding characteristics of individual HLA class I molecules. In this study, we show that polymorphisms at the HLA-B locus profoundly influence the assembly characteristics of HLA-B molecules and the stabilities of their peptide-deficient forms. In particular, dependence on the assembly factor tapasin is highly variable, with frequent occurrence of strongly tapasin-dependent or independent allotypes. Several polymorphic HLA-B residues located near the C-terminal end of the peptide are key determinants of tapasin-independent assembly. In vitro refolded forms of tapasin-independent allotypes assemble more readily with peptides compared to tapasin-dependent allotypes that belong to the same supertype, and, during refolding, reduced aggregation of tapasin-independent allotypes is observed. Paradoxically, in HIV-infected individuals, greater tapasin-independent HLA-B assembly confers more rapid progression to death, consistent with previous findings that some HLA-B allotypes shown to be tapasin independent are associated with rapid progression to multiple AIDS outcomes. Together, these findings demonstrate significant variations in the assembly of HLA-B molecules and indicate influences of HLA-B-folding patterns upon infectious disease outcomes.

Genetic variations in the KIR gene family may contribute to susceptibility to ankylosing spondylitis: a meta-analysis

The present meta-analysis of relevant case-control studies was conducted to investigate the possible relationships between genetic variations in the killer cell immunoglobulin-like receptor (KIR) gene clusters of the human KIR gene family and susceptibility to ankylosing spondylitis (AS). The following electronic databases were searched for relevant articles without language restrictions: the Web of Science, the Cochrane Library Database, PubMed, EMBASE, CINAHL, the Chinese Biomedical Database (CBM) and Chinese National Knowledge Infrastructure (CNKI) databases, covering all papers published until 2013. STATA statistical software was adopted in this meta-analysis as well. We also calculated the crude odds ratios (OR) and its 95% confidence intervals (95 % CI). Seven case-control studies with 1,004 patients diagnosed with AS and 2,138 healthy cases were implicated in our meta-analysis, and 15 genes in the KIR gene family were also evaluated. The results of our meta-analysis show statistical significance between the genetic variations in the KIR2DL1, KIR2DS4, KIR2DS5 and KIR3DS1 genes and an increased susceptibility to AS (KIR2DL1: OR 7.82, 95% CI 3.87-15.81, P< 0.001; KIR2DS4: OR 1.91, 95% CI 1.16-3.13, P = 0.010; KIR2DS5: OR1.51, 95% CI 1.14-2.01, P = 0.004; KIR3DS1: OR 1.58, 95% CI 1.34-1.86, P< 0.001; respectively). However, we failed to found positive correlations between other genes and susceptibility to AS (all P >0.05). The current meta-analysis provides reliable evidence that genetic variations in the KIR gene family may contribute to susceptibility to AS, especially for the KIR2DL1, KIR2DS4, KIR2DS5 and KIR3DS1 genes.

Know Thyself: NK-Cell Inhibitory Receptors Prompt Self-Tolerance, Education, and Viral Control

Natural killer (NK) cells provide essential protection against viral infections. One of the defining features of this lymphocyte population is the expression of a wide array of variable cell surface stimulatory and inhibitory NK receptors (sNKR and iNKR, respectively). The iNKR are particularly important in terms of NK-cell education. As receptors specific for MHC class I (MHC I) molecules, they are responsible for self-tolerance and adjusting NK-cell reactivity based on the expression level of self-MHC I. The end result of this education is twofold: (1) inhibitory signaling tunes the functional capacity of the NK cell, endowing greater potency with greater education, and (2) education on self allows the NK cell to detect aberrations in MHC I expression, a common occurrence during many viral infections. Many studies have indicated an important role for iNKR and MHC I in disease, making these receptors attractive targets for manipulating NK-cell reactivity in the clinic. A greater understanding of iNKR and their ability to regulate NK cells will provide a basis for future attempts at translating their potential utility into benefits for human health.

Killer immunoglobulin-like receptors and tumor immunity

were originally named for their capacity to elicit potent cytotoxicity against tumor cells independent of prior sensitization or gene rearrangement. This process is facilitated through the expression of activating and inhibitory receptors that provide for NK cell "education" and a subsequent ability to survey, recognize, and lyse infected or transformed cells, especially those lacking or possessing mutated MHC class I expression. Since these original observations were made, how NK cells recognize candidate target cells continues to be the topic of ongoing investigation. It is now appreciated that NK cells express a diverse repertoire of activating and inhibitory receptors of which killer immunoglobulin-like receptors (KIR) appear to play a critical role in mediating self-tolerance as well as facilitating cytotoxicity against infected or transformed cells. In addition, in the presence of an activating signal, the absence or mismatch of MHC class I molecules on such targets (which serve as inhibitory KIR ligands) promotes NK cell–mediated lysis. An increasing understanding of the complexities of KIR biology has provided recent opportunities to leverage the NK cell versus tumor effect as a novel avenue of immunotherapy for cancer. The present review summarizes the current understanding of KIR expression and function and highlights ongoing efforts to translate these discoveries into novel NK cell–mediated immunotherapies for cancer.

The role of natural cytotoxicity receptors in various pathologies: emphasis on type I diabetes

Natural killer (NK) cells are innate immune lymphocytes that function mainly as immune sentinels against viral infection and tumorigenesis. NK cell function is governed by inhibitory and activating signals arising from corresponding receptors. A prominent group of activating NK receptors is the natural cytotoxicity receptors (NCRs), which includes NKp30, NKp44, and NKp46. These receptors bind various diverse ligands of pathogenic, tumor, and even self origin. Type 1 diabetes mellitus (T1D) is a multifactorial autoimmune disease, in which insulin-producing beta (β) cells are ablated by the immune system. This killing of β cells is carried out mainly by T cells, but many other immune cells have been implicated in the pathogenesis of this disease. Importantly, NK cells were shown to be key participants in the initial autoimmune attack. It was shown that all β cells from humans and mice, healthy or sick, express an unknown ligand for the activating NKp46 receptor. In this review, we describe the role played by the NCRs in various pathologies with an emphasis on Type I diabetes.

Identification and diversity of killer cell Ig-like receptors in Aotus vociferans, a New World monkey

Previous BAC clone analysis of the Platyrrhini owl monkey KIRs have shown an unusual genetic structure in some loci. Therefore, cDNAs encoding KIR molecules from eleven Aotus vociferans monkeys were characterized here; ten putative KIR loci were found, some of which encoded atypical proteins such as KIR4DL and transcripts predicted to encode a D0+D1 configuration (AOTVOKIR2DL1*01v1) which appear to be unique in the Aotus genus. Furthermore, alternative splicing was found as a likely mechanism for producing activator receptors in A. vociferans species. KIR proteins from New World monkeys may be split into three new lineages according to domain by domain phylogenetic analysis. Although the A. vociferans KIR family displayed a high divergence among paralogous genes, individual loci were limited in their genetic polymorphism. Selection analysis showed that both constrained and rapid evolution may operate within the AvKIR family. The frequent alternative splicing (as a likely mechanism generating activator receptors), the presence of KIR4DL and KIR2DL1 (D0+D1) molecules and other data reported here suggest that the KIR family in Aotus has had a rapid evolution, independent from its Catarrhini counterparts.

Chicken NK cell receptors

Natural killer cells are innate immune cells that destroy virally infected or transformed cells. They recognize these altered cells by a plethora of diverse receptors and thereby differ from other lymphocytes that use clonally distributed antigen receptors. To date, several receptor families that play a role in either activating or inhibiting NK cells have been identified in mammals. In the chicken, NK cells have been functionally and morphologically defined, however, a conclusive analysis of receptors involved in NK cell mediated functions has not been available. This is partly due to the low frequencies of NK cells in blood or spleen that has hampered their intensive characterization. Here we will review recent progress regarding the diverse NK cell receptor families, with special emphasis on novel families identified in the chicken genome with potential as chicken NK cell receptors.

Generation of soluble NKG2D ligands: proteolytic cleavage, exosome secretion and functional implications

The activating natural killer group 2 member D (NKG2D) receptor is expressed on NK cells, cytotoxic T cells and additional T cell subsets. Ligands for human NKG2D comprise two groups of MHC class I-related molecules, the MHC class I chain-related proteins A and B (MICA/B) and 6 UL16-binding proteins (ULBP1-6). While NKG2D ligands are absent from most normal cells, expression is induced upon stress and malignant transformation. In fact, most solid tumours and leukaemia/lymphomas constitutively express at least one NKG2D ligand and thereby are susceptible to NKG2D-dependent immunosurveillance. However, soluble NKG2D ligands are released from tumour cells and can down-modulate NKG2D activation as a means of tumour immune escape. In some tumour entities, levels of soluble NKG2D ligands in the serum correlate with tumour progression. NKG2D ligands can be proteolytically shed from the cell surface or liberated from the membrane by phospholipase C in the case of glycosylphosphatidylinositol (GPI)-anchored molecules. Moreover, NKG2D ligands can be secreted in exosomal microvesicles together with other tumour-derived molecules. Depending on the specific tumour/immune cell setting, these various forms of soluble and/or exosome-bound NKG2D ligands can exert multiple effects on NKG2D/NKG2D ligand interactions. In this review, we focus on the role of various proteases in the shedding of human NKG2D ligands from tumour cells and discuss the not completely unanimous reported functional implications of soluble and exosome-secreted NKG2D ligands for immunosurveillance.

Bimodal evolution of the killer cell Ig-like receptor (KIR) family in New World primates

The immunoglobulin-like receptor (KIR) gene family in New World primates (Platyrrhini) has been characterized only in the owl monkey (Aotus sp.). To gain a better understanding of the KIR system in Platyrrhini, we analyzed a KIR haplotype in Ateles geoffroyi, and sequenced KIR complementary DNAs (cDNAs) from other three Atelidae species, Ateles hybridus, Ateles belzebuth, and Lagothrix lagotricha. Atelidae expressed a variable set of activating and inhibitory KIRs that diversified independently from their Catarrhini counterparts. They had a unique mechanism to generate activating receptors from inhibitory ones, involving a single nucleotide deletion in exon 7 and a change in the donor splice site of intron 7. The A. geoffroyi haplotype contained at least six gene models including a pseudogene, two coding inhibitory receptors, and three coding activating receptors. The centromeric region was in a tail-to-tail orientation with respect to the telomeric region. The owl monkey KIR haplotype shared this organization, and in phylogenetic trees, the centromeric genes clustered together with those of A. geoffroyi, whereas their telomeric genes clustered independently. KIR cDNAs from the other Atelidae species conformed to this pattern. Signatures of positive selection were found in residues predicted to interact with the major histocompatibility complex. Such signatures, however, primarily explained variability between paralogous genes but not between alleles in a locus. Atelidae, therefore, has expanded the KIR family in a bimodal fashion, where an inverted centromeric region has remained relatively conserved and the telomeric region has diversified by a rapid process of gene duplication and divergence, likely favored by positive selection for ligand binding.

A method for killer-cell immunoglobulin-like receptor (KIR) 3DL1/3DS1 genotyping using DNA recovered from frozen plasma

We describe a reliable and semi-automated method for killer-cell immunoglobulin-like receptor (KIR) 3DL1/S1 genotyping using DNA recovered from frozen plasma. The primers and protocol were first validated using two independent genomic DNA reference panels. To confirm the approach using plasma-derived DNA, total nucleic acids were extracted from 69 paired frozen PBMC and plasma specimens representing all common KIR3DL1/S1 genotypes (3DS1/3DS1, 3DS1/3DL1 and 3DL1/3DL1, including rare allele 3DL1*054), and analyzed in a blinded fashion. The method involves independent nested PCR amplification of KIR3DL1/S1 Exon 4, and if required Exon 3, using universal sequence-specific primers, followed by bidirectional sequencing. The free basecalling software RECall is recommended for rapid, semi-automated chromatogram analysis. KIR3DL1/S1 type assignment is based on two key nucleotide polymorphisms in Exon 4 and, if required, up to two additional polymorphisms in exon 3. Assignment can be performed manually or using our web-based algorithm, KIR3D. Extractions from plasma yielded median [IQR] nucleic acid concentrations of 0.9 [below the limit of detection-2.45] ng/μl. PCR was successful for 100% of exon 4 (69/69) and exon 3 (29/29) plasma amplifications. Chromatogram quality was high and concordance between PBMC and plasma-derived types was 100%. The estimated lower limit of input DNA required for reliable typing is 0.01 ng/μl. This method provides reliable and accurate KIR3DL1/S1 typing when conventional sources of high-quality genomic DNA are unavailable or limiting.

Are killer cell immunoglobulin-like receptor genes important for the prediction of kidney graft rejection?

Killer cell immunoglobulin-like receptors (KIRs) are expressed on natural killer cells and minor subpopulations of thymus-derived (T) lymphocytes. KIRs may have a long cytoplasmic tail and inhibit cell activation upon ligand (HLA class I) binding, or they may have a short cytoplasmic tail and activate a cell after ligand binding. They are encoded by up to 14 genes present in different individuals in different combinations, whence their associations with several human diseases. KIR involvement in the fate of kidney allograft has not been extensively studied; nevertheless some associations had already been noticed. Their results are not concordant: some authors found no effect of KIR genotype, whereas others detected protective effect of KIR2DL2/KIR2DS2 or KIR-KIR ligand mismatch. We found an association of KIR2DS4 gene with acute rejection and a protective effect of KIR2DS5 gene. Interestingly, in patients, whose end-stage renal disease was caused by glomerulonephritis, the effect of KIR2DS4 was stronger than HLA mismatch, whereas opposite was true for recipients with other causes of renal failure.

No impact of KIR-ligand mismatch on allograft outcome in HLA-compatible kidney transplantation

Natural killer (NK) cell function can be modulated by the killer cell immunoglobulin-like receptors (KIR) which interact with human leukocyte antigen (HLA) class I molecules on target cells. KIR-ligand mismatching has recently been shown by van Bergen et al. (American Journal of Transplantation 2011; 11(9): 1959-1964) to be a significant risk factor for long-term graft loss in HLA-A, -B and -DR compatible kidney transplants. To verify this potentially important finding, we performed genotyping of 608 deceased-donor kidney graft recipients and their HLA-A, -B and -DR compatible donors for KIR and HLA, using samples and clinical data provided by the Collaborative Transplant Study. Graft survival of KIR-ligand-matched and -mismatched transplants was compared. We found no impact of KIR-ligand mismatching on 10-year graft survival in HLA-A, -B, -DR compatible kidney transplants. Further analysis did not reveal a significant effect of recipient activating/inhibitory KIR or KIR genotypes on graft survival. Our data do not support the concept that KIR-HLA matching might serve as a tool to improve long-term renal allograft survival.

HSV-2 specifically down regulates HLA-C expression to render HSV-2-infected DCs susceptible to NK cell killing

Both NK cells and CTLs kill virus-infected and tumor cells. However, the ways by which these killer cells recognize the infected or the tumorigenic cells are different, in fact almost opposite. CTLs are activated through the interaction of the TCR with MHC class I proteins. In contrast, NK cells are inhibited by MHC class I molecules. The inhibitory NK receptors recognize mainly MHC class I proteins and in this regard practically all of the HLA-C proteins are recognized by inhibitory NK cell receptors, while only certain HLA-A and HLA-B proteins interact with these receptors. Sophisticated viruses developed mechanisms to avoid the attack of both NK cells and CTLs through, for example, down regulation of HLA-A and HLA-B molecules to avoid CTL recognition, leaving HLA-C proteins on the cell surface to inhibit NK cell response. Here we provide the first example of a virus that through specific down regulation of HLA-C, harness the NK cells for its own benefit. We initially demonstrated that none of the tested HSV-2 derived microRNAs affect NK cell activity. Then we show that surprisingly upon HSV-2 infection, HLA-C proteins are specifically down regulated, rendering the infected cells susceptible to NK cell attack. We identified a motif in the tail of HLA-C that is responsible for the HSV-2-meduiated HLA-C down regulation and we show that the HLA-C down regulation is mediated by the viral protein ICP47. Finally we show that HLA-C proteins are down regulated from the surface of HSV-2 infected dendritic cells (DCs) and that this leads to the killing of DC by NK cells. Thus, we propose that HSV-2 had developed this unique and surprising NK cell-mediated killing strategy of infected DC to prevent the activation of the adaptive immunity.

Approximately 20% of all humans are latently and asymptomatically infected with HSV-2. This suggests that the virus developed mechanisms to avoid immune cell detection; many of which are still unknown. Infected cells are killed mainly by two lymphocyte populations; NK cells and CTLs that belong to the innate and the adaptive immunity, respectively. While the killing machinery of these two cell types is similar, almost identical, the ways by which they discriminate between infected and uninfected cells is different. CTLs are activated, primarily by DCs, to become effector cells. They then recognize virus-derived peptides in the groove of MHC class I molecules and eliminate the virally infected cells. In contrast, NK cells recognize infected cells through several NK cell activating receptors, while the recognition of MHC class I proteins by NK cells leads to inhibition of NK cell killing. Viruses, such as HIV, developed mechanisms to interfere with the function of both NK cells and CTLs via targeting of specific MHC class I proteins. Here we show that HSV-2 developed a MHC class I-dependent mechanism in which the virus, through specific targeting of HLA-C by the viral protein ICP47, harness the NK cells for its own benefit, probably to avoid the activation of adaptive immune response.

Monoclonal antibody-based immunotherapy for multiple myeloma

Multiple myeloma (MM) is a life-threatening hematological malignancy. High-dose chemotherapy followed by autologous stem cell transplantation is a relatively effective treatment, but disease recurrence remains a major obstacle. Allogeneic transplantation may result in durable responses and cure due to antitumor immunity mediated by donor lymphocytes. However, morbidity and mortality related to graft-versus-host disease remain a challenge. Recent advances in understanding the interaction between the immune system of the patient and the malignant cells are influencing the design of clinically more efficient study protocols for MM. This review will focus on MM antigens and their specific antibodies. These monoclonal antibodies are an attractive therapeutic tool for MM humoral immunotherapy, with most promising preclinical results.

Killer cell immunoglobulin-like receptor gene associations with autoimmune and allergic diseases, recurrent spontaneous abortion, and neoplasms

Killer cell immunoglobulin-like receptors (KIRs) are a family of cell surface inhibitory or activating receptors expressed on natural killer cells and some subpopulations of T lymphocytes. KIR genes are clustered in the 19q13.4 region and are characterized by both allelic (high numbers of variants) and haplotypic (different numbers of genes for inhibitory and activating receptors on individual chromosomes) polymorphism. This contributes to diverse susceptibility to diseases and other clinical situations. Associations of KIR genes, as well as of genes for their ligands, with selected diseases such as psoriasis vulgaris and atopic dermatitis, rheumatoid arthritis, recurrent spontaneous abortion, and non-small cell lung cancer are discussed in the context of NK and T cell functions.