Increased activating killer immunoglobulin-like receptor genes and decreased specific HLA-C alleles in couples with recurrent spontaneous abortion

Accumulating evidence indicates natural killer (NK) cells play crucial roles in successful pregnancy. To investigate whether the killer cell immunoglobulin-like receptor (KIR) gene polymorphism and the corresponding specific HLA ligands in parent couples possessing a susceptibility to unexplained recurrent spontaneous abortion (RSA), we searched 73 pairs of childless couples with three or more abortions characterized as unexplained RSA and 68 pairs of healthy control couples. Peripheral blood was drawn to obtain genomic DNA which was used for a polymerase chain reaction using sequence-specific primers (PCR-SSP) in order to determine whether 15 selected KIR genes and two groups of HLA-C alleles were present. Our result showed that gene frequency of KIR2DS1 was higher in patients with RSA compared to that of control subjects (P =0.029). Increased numbers of activating KIR genes was observed in patients (P =0.041). Women who possessed more than two activating KIR genes were found more frequently in patients than those in control subjects (P =0.018). From a cohort of husband and wife couples, the women with a KIR2DS1 gene, and with a decreased group 2 HLA-C allele for the homologous inhibitory receptor KIR2DL1, had a tendency to fall into the RSA group (P =0.004). The results suggest that a genetic variation at the KIR locus influences the susceptibility to unexplained RSA in the Chinese Han population. Moreover, decreased ligands for inhibitory KIRs could potentially lower the threshold for NK cell activation, mediated through activating receptors, thereby contributing to pathogenesis of RSA.     

KIR/HLA combination associated with the risk of complications in celiac disease

The pathogenesis of celiac disease (CD) is associated with polymorphisms in human leukocyte antigen (HLA) genes; however, compelling evidence suggests that additional non-HLA genes are associated with CD and related complications. The present study investigated whether killer cell immunoglobulin-like receptor (KIR)/HLA gene combinations are associated with CD and its clinical complications in the population of northeast Italy. The study included 61 adults affected by CD: 48 patients were at first diagnosis and 13 patients had CD-related complications (8 with refractory CD and 5 with cancer). Controls were 69 blood donors genotyped for KIR and HLA. Several statistically significant differences emerged between CD patients and blood donors. The results herein presented show that susceptibility to CD with refractory disease or cancer is associated with various genotypes including the 2DS2/2DL2+C1, 2DS3, 3DL1, and 2DL5B genes. In addition, the absence of the Bw4 ligand may be a predisposing factor for cancer. These results suggest that a KIR haplotype and HLA ligands may be involved in the susceptibility to important clinical CD complications such as tumors or refractoriness as a result of a gluten-free diet.     

Killer Cell Immunoglobulin-like Receptors and Their HLA Ligands are Related with the Immunopathology of Chagas Disease

The aim of this study was to investigate the influence of killer cell immunoglobulin-like receptor (KIR) genes and their human leucocyte antigen (HLA) ligands in the susceptibility of chronic Chagas disease. This case-control study enrolled 131 serologically-diagnosed Chagas disease patients (59 men and 72 women, mean age of 60.4 ± 9.8 years) treated at the University Hospital of Londrina and the Chagas Disease Laboratory of the State University of Maringa. A control group was formed of 165 healthy individuals - spouses of patients or blood donors from the Regional Blood Bank in Maringa (84 men and 81 women, with a mean age of 59.0 ± 11.4 years). Genotyping of HLA and KIR was performed by PCR-SSOP. KIR2DS2-C1 in the absence of KIR2DL2 (KIR2DS2⁺/2DL2^-/C1⁺) was more frequent in Chagas patients (P = 0.020; Pc = 0.040; OR = 2.14) and, in particular, those who manifested chronic chagasic cardiopathy—CCC (P = 0.0002; Pc = 0.0004; OR = 6.64; 95% CI = 2.30–18.60) when compared to the control group, and when CCC group was compared to the patients without heart involvement (P = 0.010; Pc = 0.020; OR = 3.97). The combination pair KIR2DS2⁺/2DL2^-/KIR2DL3⁺/C1⁺ was also positively associated with chronic chagasic cardiopathy. KIR2DL2 and KIR2DS2 were related to immunopathogenesis in Chagas disease. The combination of KIR2DS2 activating receptor with C1 ligand, in the absence of KIR2DL2, may be related to a risk factor in the chronic Chagas disease and chronic chagasic cardiopathy.     

Activated lymphocytes during acute Epstein-Barr virus infection

Activated lymphocytes, as identified by HLA-DR expression, associated with acute Epstein-Barr virus (EBV)-induced infectious mononucleosis (IM) were shown to be a heterogeneous population containing significantly elevated cytotoxic/suppressor (CD8) T cells, natural killer (CD16) cells and helper (CD4) T cells. CD8 T cells were the primary activated population representing 24.5% of the total lymphocyte population. The activated CD4 T cells and natural killer cells accounted for 6.7% and 3.5% of the total lymphocyte population, respectively. Analysis of serum soluble interleukin 2 receptors (IL-2R) demonstrated significantly (p less than 0.001) elevated levels in the serum of acute IM patients compared with normal controls. Elevated levels of serum IL-2R were correlated (r = 0.67) with increased percentages of Leu 2a+/HLA-DR+T cells (i.e., activated CD8 T cells). Patients with X-linked lymphoproliferative syndrome and virus-associated hemophagocytic syndrome, two syndromes associated with severe acute EBV infections, demonstrated the most dramatic increase in serum IL-2R levels. These data demonstrate that EBV is associated with intense immune stimulation and that during acute IM activated lymphocytes, other than the CD8 T cells, may contribute to the immune response to EBV.     

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The antiviral action of natural killer (NK) cells is regulated by a wide repertoire of germ-line encoded membrane receptors which recognize the expression of certain self-molecules on target cells. Among the receptors, killer cell immunoglobulin-like receptor (KIR) which recognizes the expression of human leukocyte antigen (HLA) class I has a predominant role in regulating the effector functions of NK cells, particularly in viral infections. We studied a total of 128 hepatitis B virus (HBV) patients (15 acute, 43 asymptomatic, 27 chronic and 43 with other liver diseases) while attending the Department of Medical Gastroenterology, Government Rajaji Hospital, Madurai, India, and 128 ethnic matched control to find the association between the KIR : HLA genes and differential manifestations of HBV. KIR and its ligand HLA polymorphism were identified by DNA-PCR methods. The activatory receptor KIR-2DS1 was significantly elevated in various disease categories, namely asymptomatic, chronic and other HBV, except acute HBV infection. Whereas, KIR 2DS3 in acute and chronic patients and KIR 2DS5 and 3DS1 in asymptomatic individuals. Among various KIR–HLA combinations, homozygous 2DS2:C1 and individuals with 3DSI:BW4 (OR = 3.23, CI = 1.55–6.7, Pc = 0.02) are associated with HBV asymptomatism, while most of the two domain inhibitory receptors with their ligands showed significant risk in other liver diseases. Further, KIR3DL1 : HLA Bw4Iso80 (OR = 3.89, 95% CI = 1.58–9.55, Pc = 0.004) is related with higher risk for asymptomatic infection when compared with chronic HBV. Thus, the select KIR : HLA alleles and combinations seem to direct the NK cell activities and immune response in different directions resulting in varied symptoms and manifestations in the subgroups of HBV-infected patients studied.     

Association of killer cell immunoglobulin-like receptor polymorphisms with chronic hepatitis C and responses to therapy in Brazil

Soroprevalence for Hepatitis C virus is reported as 2.12% in Northern Brazil, with about 50% of the patients exhibiting a sustained virological response (SVR). Aiming to associate polymorphisms in Killer Cell Immunoglobulin-like Receptors (KIR) with chronic hepatitis C and therapy responses we investigated 125 chronic patients and 345 controls. Additionally, 48 ancestry markers were genotyped to control for population stratification. The frequency of the KIR2DL2 and KIR2DL2+HLA-C^Asp80 gene and ligand was higher in chronic infected patients than in controls (p < 0.0009, OR = 3.4; p = 0.001, OR = 3.45). In fact, KIR2DL3 is a weaker inhibitor of NK activity than KIR2DL2, which could explain the association of KIR2DL2 with chronic infection. Moreover, KIR2DS2 and KIR2DS2+HLA-C^Asp80 (p < 0.0001, OR = 2.51; p = 0.0084, OR = 2.62) and KIR2DS3 (p < 0.0001; OR = 2.57) were associated with chronic infection, independently from KIR2DL2. No differences in ancestry composition were observed between control and patients, even with respect to therapy response groups. The allelic profile KIR2DL2/KIR2DS2/KIR2DS3 was associated with the chronic hepatitis C (p < 0.0001; OR = 3). Furthermore, the patients also showed a higher mean number of activating genes and a lower frequency of the homozygous AA profile, which is likely secondary to the association with non-AA and/or activating genes. In addition, the KIR2DS5 allele was associated with SVR (p = 0.0261; OR = 0.184).The ancestry analysis of samples ruled out any effects of population substructuring and did not evidence interethnic differences in therapy response, as suggested in previous studies.     

Copy number variation of KIR genes influences HIV-1 control

A genome-wide screen for large structural variants showed that a copy number variant (CNV) in the region encoding killer cell immunoglobulin-like receptors (KIR) associates with HIV-1 control as measured by plasma viral load at set point in individuals of European ancestry. This CNV encompasses the KIR3DL1-KIR3DS1 locus, encoding receptors that interact with specific HLA-Bw4 molecules to regulate the activation of lymphocyte subsets including natural killer (NK) cells. We quantified the number of copies of KIR3DS1 and KIR3DL1 in a large HIV-1 positive cohort, and showed that an increase in KIR3DS1 count associates with a lower viral set point if its putative ligand is present (p = 0.00028), as does an increase in KIR3DL1 count in the presence of KIR3DS1 and appropriate ligands for both receptors (p = 0.0015). We further provide functional data that demonstrate that NK cells from individuals with multiple copies of KIR3DL1, in the presence of KIR3DS1 and the appropriate ligands, inhibit HIV-1 replication more robustly, and associated with a significant expansion in the frequency of KIR3DS1+, but not KIR3DL1+, NK cells in their peripheral blood. Our results suggest that the relative amounts of these activating and inhibitory KIR play a role in regulating the peripheral expansion of highly antiviral KIR3DS1+ NK cells, which may determine differences in HIV-1 control following infection.     

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.     

Killer Cell Immunoglobulin-Like Receptor Genes and their HLA-C Ligands in Hashimoto Thyroiditis in a Chinese Population

Objective: Natural killer (NK) cells serve as primary immune surveillance and are partially regulated by combinations of killer immunoglobulin-like receptors (KIR) and their human leukocyte antigen-C (HLA-C) ligands. Alterations in NK cell activity have been associated with Hashimoto thyroiditis (HT). The aim of this study was to determine whether certain KIR/HLA-C genotype combinations play a role in HT pathogenesis.Methods: The present study enrolled 107 unrelated HT patients and 108 random healthy individuals in a case-control study. Blood was collected for DNA extraction; typing of KIR genes and HLA-C alleles was performed by polymerase chain reaction with sequence specific primers (PCR-SSP), followed by electrophoresis on agarose gels.Results: Among a panel of KIR2D/HLA-C genotype combinations, the frequency of KIR2DS2/HLA-C1 was significantly increased in HT patients compared to controls (33.64% vs. 12.96%, P<.001). To further analyze the precise genotype, we investigated inhibitory or activating KIR/HLA-C gene pairs when their corresponding activating or inhibitory KIR genes were absent in the 2 groups. Only the frequency of KIR2DS2(-)2DL2/3(+)HLA-C1(+) was significantly decreased in HT patients compared to controls (48.60% vs. 70.37%, P = .001).Conclusion: Our data suggest that KIR2DS2/HLA-C1 may correlate with HT pathogenesis. On the contrary, the predominance of KIR2DL2/3/HLA-C1 in the absence of KIR2DS2 suggests a potential inhibitory role in HT pathogenesis. In conclusion, our findings may further elucidate the mechanisms underlying the pathogenesis of HT and other autoimmune diseases.Abbreviations:HLA-C = human leukocyte antigen-CHT = Hashimoto thyroiditisKIR = killer immunoglobulin-like receptorNK = natural killerPCR = polymerase chain reaction     

Activating KIR and HLA Bw4 ligands are associated to decreased susceptibility to pemphigus foliaceus, an autoimmune blistering skin disease

The KIR genes and their HLA class I ligands have thus far not been investigated in pemphigus foliaceus (PF) and related autoimmune diseases, such as pemphigus vulgaris. We genotyped 233 patients and 204 controls for KIR by PCR-SSP. HLA typing was performed by LABType SSO reagent kits. We estimated the odds ratio, 95% confidence interval and performed logistic regression analyses to test the hypothesis that KIR genes and their known ligands influence susceptibility to PF. We found significant negative association between activating genes and PF. The activating KIR genes may have an overlapping effect in the PF susceptibility and the presence of more than three activating genes was protective (OR=0.49, p=0.003). A strong protective association was found for higher ratios activating/inhibitory KIR (OR=0.44, p=0.001). KIR3DS1 and HLA-Bw4 were negatively associated to PF either isolated or combined, but higher significance was found for the presence of both together (OR=0.34, p<10(-3)) suggesting that the activating function is the major factor to interfere in the PF pathogenesis. HLA-Bw4 (80I and 80T) was decreased in patients. There is evidence that HLA-Bw4(80T) may also be important as KIR3DS1 ligand, being the association of this pair (OR=0.07, p=0.001) stronger than KIR3DS1-Bw4(80I) (OR=0.31, p=0.002). Higher levels of activating KIR signals appeared protective to PF. The activating KIR genes have been commonly reported to increase the risk for autoimmunity, but particularities of endemic PF, like the well documented influence the environmental exposure in the pathogenesis of this disease, may be the reason why activated NK cells probably protect against pemphigus foliaceus.     

Killer Cell Immunoglobulin-Like Receptor Alleles Alter HIV Disease in Children

Background

HLA class I molecules are ligands for killer cell immunoglobin like receptors (KIR) that control the antiviral response of natural killer (NK) cells. However, the effects of KIR and HLA (KIR/HLA) alleles on HIV disease of children have not been studied.

Methods

993 antiretroviral naïve children with symptomatic HIV infection from PACTG protocols P152 and P300 were genotyped for KIR and HLA alleles using the Luminex platform. Linear regression was used to test the association between genotypes and baseline pre-ART HIV RNA, CD4⁺ lymphocyte count, and cognitive score, adjusting for age, race/ethnicity and study. The interaction between genetic markers and age was investigated. To account for multiple testing the false discovery rate (FDR) was controlled at 0.05.

Results

Children with the KIR2DS4*ALL FULL LENGTH (KIR2DS4*AFL) allele had higher CD4⁺ lymphocyte counts. Among children ≤2 years of age, the KIR2DS4*AFL was associated with lower plasma HIV RNA and higher cognitive index scores. KIR Cent2DS3/5_1 had lower CD4⁺ lymphocyte counts in children ≤2 years of age, while the presence of Tel1, Tel2DS4_2, Tel2DS4_4, Tel8, Tel2DS4_6 had higher CD4⁺ lymphocyte counts in all children. Presence of Cent2, Cent4 and Cent8 was associated with increased HIV RNA load in children ≤2 years. Presence of KIR3DL1+Bw4 was associated with higher CD4⁺ lymphocyte counts in all children. Among children >2 years old, KIR3DS1+Bw4-80I was associated with higher plasma HIV RNA, and Bw6/Bw6 was associated with lower plasma HIV RNA compared to children with KIR3DS1+Bw4-80I.

Conclusions

Presented data show for the first time that specific KIR alleles independently or combined with HLA ligands are associated with HIV RNA and CD4⁺ lymphocyte counts in infected, antiretroviral naive children; and many of these effect estimates appear to be age dependent. These data support a role for specific KIR alleles in HIV pathogenesis in children.     

Association of killer cell immunoglobulin-like receptors with pulmonary tuberculosis in Chinese Han

Killer cell immunoglobulin-like receptors (KIRs) are involved in the pathogenesis of a variety of diseases. However, whether KIR polymorphism is associated with susceptibility to pulmonary tuberculosis was unknown. We examined a possible association of KIR polymorphism with susceptibility to pulmonary tuberculosis in Chinese Han. We analyzed 15 KIR genes in 109 pulmonary tuberculosis patients and 110 healthy controls using sequence-specific primer PCR analysis of genomic DNA. We found that the frequencies of KIR2DS1, 2DS3 and 3DS1 were significantly higher in patients than in the control group. In addition, the number of subjects carrying more than two activating KIR genes in the patient group was significantly higher than in the control group. The gene cluster containing KIR3DS1-2DL5-2DS1-2DS5 was also significantly more frequent in the patient group. In conclusion, KIR genes 2DS1, 2DS3 and 3DS1 appear to be associated with resistance to pulmonary tuberculosis in the Chinese Han population. KIR genes apparently have a role in resistance to pulmonary tuberculosis.     

Contribution of KIR3DL1/3DS1 to ankylosing spondylitis in human leukocyte antigen-B27 Caucasian populations

Killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) loci are both highly polymorphic, and some HLA class I molecules bind and trigger cell-surface receptors specified by KIR genes. We examined whether the combination of KIR3DS1/3DL1 genes in concert with HLA-B27 genotypes is associated with susceptibility to ankylosing spondylitis (AS). Two HLA-B27-positive Caucasian populations were selected, one from Spain (71 patients and 105 controls) and another from the Azores (Portugal) (55 patients and 75 controls). All were typed for HLA-B and KIR (3DS1 and 3DL1) genes. Our results show that in addition to B27, the allele 3DS1 is associated with AS compared with B27 controls (p < 0.0001 and p < 0.003 in the Spanish population and Azoreans, respectively). We also observed that the association of KIR3DS1 to AS was found in combination with HLA-B alleles carrying Bw4-I80 in trans position in the Spanish population (30.9% in AS versus 15.2% in B27 controls, p = 0.02, odds ratio (OR) = 2.49) and in Azoreans (27.2% in AS versus 8.7% in B27 controls, p = 0.01, OR = 4.4 in Azoreans). On the other hand, 3DL1 was decreased in patients compared with B27 controls (p < 0.0001 in the Spanish population and p < 0.003 in Azoreans). The presence of this allele in combination with Bw4-I80 had a protective effect against the development of AS in the Spanish population (19.7% in AS, 35.2% in B27 controls; p = 0.03, OR = 0.45). The presence of KIR3DS1 or KIR3DL1 in combination with HLA-B*27s/HLA-B Bw4-I80 genotypes may modulate the development of AS. The susceptibility to AS could be determined by the overall balance of activating and inhibitory composite KIR-HLA genotypes.     

Polymorphism of killer cell immunoglobulin-like receptors (KIR) and their HLA ligands in Graves’ disease

Killer immunoglobulin-like receptors (KIR) play a pivotal role in commencement of both innate and adaptive immunity. Dysregulation of KIRs is associated with an increased risk of autoimmune disorders. This study was designed to assess whether polymorphisms in KIR gene family and their respective HLA class I ligands confer protection or susceptibly to Graves’ disease (GD). Eighty patients with confirmed GD (cases) and 176 healthy unrelated subjects (controls) were recruited. Using a polymerase chain reaction sequence-specific primer directed method (PCR-SSP), presence or absence of KIR genes and their HLA ligands were determined. No significant differences were observed between case and control groups regarding individual KIR gene frequencies (p > 0.05 in all cases). The frequency of group A haplotype (the most common KIR haplotype, encompassing 2DL1/2DL3/3DL1/2DS4/2DP1/3DP1/2DL4/3DL2/3DL3), was not different between individuals with and without GD. Moreover, among all other haplotypes (group Bx), no significant differences regarding distribution of centromeric and telomeric gene clusters were identifiable. Inhibitory/activatory gene contents were also comparable between the two groups. Four models of KIR-HLA interaction (inhibition, activation, unrestrained inhibition, and unrestrained activation) were constructed. No combination proved to confer susceptibility to, or offer protection against GD. It seems that the contribution of KIR gene polymorphism to natural killer cell dysfunction and other autoimmune abnormalities observed in GD is limited.     

Self-association of an activating natural killer cell receptor, KIR2DS1

As a major component of the innate immune system, natural killer cells are responsible for activating the cytolytic killing of certain pathogen-infected or tumor cells. The self-recognition of natural killer cells is achieved in part by the killer cell immunoglobulin-like receptors (KIRs) protein family. In the current study, using a suite of biophysical methods, we investigate the self-association of an activating KIR, KIR2DS1. This KIR is of particular interest because when in the presence of the HLA-Cw6 protein, KIR2DS1 becomes a major risk factor for psoriasis, an autoimmune chronic skin disease. Using circular dichroism spectroscopy, dynamic light scattering, and atomic force microscopy, we reveal that KIR2DS1 self-associates in a well-defined fashion. Our novel results on an activating KIR allow us to suggest a working model for the KIR2DS1- HLA class I molecular mechanism.     

Linkage disequilibrium organization of the human KIR superlocus: implications for KIR data analyses

An extensive family-based study of linkage disequilibrium (LD) in the killer cell immunoglobulin-like receptors (KIR) cluster was performed. We aimed to describe the LD structure in the KIR gene cluster using a sample of 418 founder haplotypes identified by segregation in a group of 106 families from Northern Ireland. The LD was studied at two levels of polymorphism: the structural level (presence or absence of KIR genes) and the allelic level (between alleles of KIR genes). LD was further assessed using the predictive value of one KIR polymorphism for another one in order to provide an interpretative framework for the LD effect in association studies. In line with previous research, distinct patterns of KIR genetic diversity within the genomic region centromeric to KIR2DL4 (excluding KIR2DL4) and within the telomeric region including KIR2DL4 were found. In a comprehensive PPV/NPV-based LD analysis within the KIR cluster, robust tag markers were found that can be used to identify which genes are concomitantly present or absent and to further identify groups of associated KIR alleles. Several extended KIR haplotypes in the study population were identified (KIR2DS2*POS-KIR2DL2*001-KIR2DL5B*002-KIR2DS3*00103-KIR2DL1*00401; KIR2DL4*011-KIR3DL1/S1*005-KIR2DS4*003-KIR3DL2*003; KIR2DL4*00802-KIR3DL1/S1*004-KIR2DS4*006-KIR3DL2*005; KIR2DL4*00801-KIR3DL1/S1*00101-KIR2DS4*003-KIR3DL2*001; KIR2DL4*00103-KIR3DL1/S1*008-KIR2DS4*003-KIR3DL2*009; KIR2DL4*00102-KIR3DL1/S1*01502/*002-KIR2DS4*00101-KIR3DL2*002; KIR2DL4*00501-KIR3DL1/S1*013-KIR2DL5A*001-KIR2DS5*002-KIR2DS1*002-KIR3DL2*007). The present study provides a rationale for analyzing associations of KIR polymorphisms by taking into account the complex LD structure of the KIR region.     

Killer immunoglobulin‐like receptor repertoire analysis in a Caucasian Spanish cohort with inflammatory bowel disease

Immunological molecules are implicated in inflammatory disorders, including inflammatory bowel disease (IBD; Crohn disease [CD] and ulcerative colitis [UC]). Killer cell immunoglobulin‐like receptors (KIRs) are also genetically variable proteins involved in immune function. They are expressed by NK cells and certain T lymphocytes, regulate specificity and function by interaction with HLA Class I molecules, may be either inhibitory or activating and are polymorphic both in terms of alleles and haplotype gene content. Genetic associations between activating KIRs and certain autoimmune and inflammatory diseases have been reported; however, a possible association between KIR and IBD remains unclear. The aim of this study was to determine the relationship between KIR repertoire and IBD pathologies in a Spanish cohort. KIR variability was analyzed using PCR–sequence specific oligonucleotide probes (SSOP). Inhibitory KIR2DL5 was found more frequently in UC and IBD patient groups than in healthy controls (P = 0.028 and P = 0.01, respectively), as was activating KIR2DS1 (P = 0.02, Pc > 0.05, UC vs. Controls; P = 0.001, Pc = 0.01, IBD vs Controls; P = 0.01, Pc > 0.05, Controls vs CR), KIR2DS5 (P = 0.0028, Pc = 0.04, Controls vs UC; P = 0.0001, Pc = 0.0017, Controls vs IBD; P = 0.01, Pc > 0.05, Controls vs CD) and KIR3DS1 (P = 0.012, Pc > 0.05, Controls vs IBD). Our data suggest that imbalance between activating and inhibitory KIR may partially explain the different pathogeneses of these IBDs and that there is a hypothetical role for the telomeric B region (which contains both KIR2DS5 and KIR2DS1) in these diseases.     

Detection of KIR3DS1 on the cell surface of peripheral blood NK cells facilitates identification of a novel null allele and assessment of KIR3DS1 expression during HIV-1 infection

KIR3DL1 is a highly polymorphic killer cell Ig-like receptor gene with at least 23 alleles described, including its activating counterpart, KIR3DS1. Recently, the KIR3DS1 allele has been shown to slow progression to AIDS in individuals expressing HLA-Bw4 with isoleucine at position 80. However, due to the lack of a specific Ab, KIR3DS1 expression and function is not well characterized. In this study, we demonstrate KIR3DS1 expression on a substantial subset of peripheral natural killer cells through its recognition by the mAb Z27. The fidelity of this detection method was confirmed by analysis of KIR3DS1 transfectants and the identification of a novel KIR3DS1 null allele. Interestingly, KIR3DS1 is also expressed by a small proportion of CD56(+) T cells. We show that ligation of KIR3DS1 by Z27 leads to NK cell IFN-gamma production and degranulation as assessed by expression of CD107a. Furthermore, we document the persistence of KIR3DS1(+) NK cells in HIV-1 viremic patients. The high frequency of KIR3DS1 expression, along with its ability to activate NK cells, and its maintenance during HIV-1 viremia are consistent with the epidemiological data suggesting a critical role for this receptor in controlling HIV-1 pathogenesis.     

Genetic polymorphism of NK receptors and their ligands in melanoma patients: prevalence of inhibitory over activating signals

Antitumor cytotoxicity of NK cells and T cells expressing NK-associated receptors is regulated by interaction between their cell surface killer immunoglobulin-like receptors (KIRs) and CD94/NKG2 heterodimers with MHC class I ligands on target cells. To test the hypothesis that KIR and/or HLA polymorphisms, and KIR/HLA combinations could contribute to the tumorigenesis, association studies were performed in 50 patients with malignant melanoma (MM) in different stages of disease and 54 controls. Our data showed that the frequency of inhibitory and activating KIR genes and KIR genotypes did not differ significantly between healthy individuals and melanoma patients. HLA haplotype distribution showed statistically significant increased frequencies of A*01-B*35-Cw*04 (0.069 vs 0.000; pc<0.05; OR=19.9), A*01-B*08-DRB1*03 (0.079 vs 0.019; pc<0.05; OR=4.5), and A*24-B*40-DRB1*11 (0.026 vs 0.000; pc<0.05; OR=7.1) in melanoma patients compared with healthy controls. Individuals homozygous for group 2 HLA-C ligands were less frequent in the patient group compared with the control cohort (12% vs 31.5%; p<0.017). In addition, we observed an increased frequency (88.0% vs 68.5%; p=0.017; OR=2.80) of KIR2DL2/2DL3 in combination with their group 1 HLA-C ligands, while the presence of these KIRs in the absence of the putative ligands was decreased (12.0% vs 31.5%; p=0.017) in the patient group. Furthermore, an increased frequency of activating KIR2DS1 in the absence of the putative HLA-C^Lys80 ligands was found in melanoma patients (16.0% vs 9.2%). In contrast, KIR2DS2 was absent in patients more often (38.0% vs 25.9%) when the presumptive HLA-C^Asn80 ligands were present. A slightly higher incidence of KIR3DL1 in combination with the less effective Bw4^Thr80 ligands was seen in patients with primary (20.8%) compared with metastatic (4.2%) disease. The data obtained in this study imply that there may not be a direct association between KIR gene content in the genome and the presence of malignant melanoma, or melanoma progression. However, some HLA haplotypes could be predisposing to MM in the Bulgarian population. Furthermore, distinct KIR/HLA ligand combinations may be relevant to the development of malignancy whereby inhibition overrides activation of NK cells and T cells expressing NK-associated receptors, which in turn might facilitate tumor escape and progression.