Natural killer cell crossmatch: functional analysis of inhibitory killer immunoglobulin-like receptors and their HLA ligands

Attempts to predict outcome of bone marrow transplantation based on killer immunoglobulin-like receptor (KIR) and HLA genotyping have yielded discordant results. To better understand the factors involved, we investigated natural killer (NK) cell function and correlated it with genetics and expression of inhibitory KIR and HLA ligands in 20 normal allogeneic pairs. KIR expression was analyzed by flow cytometry to estimate the percentage of NK cells that could be inhibited by the HLA ligands in each pair combination. NK cytotoxicity against ConA blasts demonstrated a positive correlation between the number of KIR/HLA matches and the predicted number of NK cells that could be inhibited. When 50% or more of the NK cells could be inhibited, cytotoxicity was lower (8%) than when 25% or less of the NK cells expressed KIR with matched HLA (49%) (p < 0.0001). Our data suggest that the interaction between inhibitory KIR and HLA ligands can be correlated to some extent with NK cell function, but measurement of NK activity may provide the best information for analysis of clinical situations.     

HLA association with hepatitis C virus infection

Hepatitis is one of the most important infectious diseases in Thailand. The knowledge of host factors that influence the course of the disease is still limited. In this study, the HLA class I and class II phenotypes were analyzed in the 2 groups of HCV-infected Thai populations. The first group included 43 individuals with transient HCV infection (HCV antibody positive, HCV RNA PCR negative), and the second included 57 individuals with persistent chronic HCV infection (HCV antibody positive, PCR positive). HLA class I typing was performed by 2-stage microlymphocytotoxicity test, and HLA class II typing, by PCR-SSO. No significant difference in the frequencies of HLA-A and -B antigens was observed between the 2 groups of HCV-infected individuals. The frequency of DRB1*0301 and DQB1*0201 was significantly higher in the persistent-infection group than in the transient-infection group (Pc = 0.03, Pc = 0.04, respectively). In addition, DRB1*0701 and DQA1*0201 were significantly decreased in all the HCV-infected patients compared with levels in the normal controls (Pc = 0.003, Pc = 0.001, respectively). This study demonstrated that DRB1*0301 and DQB1*0201 are associated with persistent HCV infection, whereas DRB1*0701 and DQA*0201 are associated with protection against HCV infection.     

HLA class II alleles and chronic hepatitis C virus infection

The aim of this study was to investigate association of human leucocyte antigens (HLA)-DRB1 and DQB1 polymorphisms with hepatitis C virus (HCV) infection and with the occurrence of severe liver fibrosis/cirrhosis in chronically infected patients. Ninety-nine white patients, from southeast Brazil, with confirmed HCV chronic infection were included in the study. Severe fibrosis/cirrhosis (METAVIR scores F3-F4) was present in 49 patients. HLA-DRB1 specificities and DRB1*11 and DQB1* alleles were determined by PCR-SSP, and their frequencies were compared between patients and a control group of 103 healthy white Brazilian individuals. The results confirmed previous reports of the association of DRB1*11 and DQB1*03 with protection from chronic HCV infection, but did not confirm their association with protection from severe fibrosis/cirrhosis. Furthermore, the results suggested that the polymorphic sites on HLA molecules responsible for protection from chronic HCV infection are encoded not only by the DRB1*1101 and DQB1*0301, as suggested in the literature, but also by other DRB1*11 and DQB1*03 alleles. Thus, we hypothesized that the common polymorphic residues shared by different DRB1*11 and/or DQB1*03 alleles might be responsible for selection of viral epitopes for presentation to CD4(+) T cells, leading to an efficient immune response against the virus.     

Association between chronic hepatitis C virus infection and cryoglobulinemia

Hepatitis C virus infection (HCV) causes both acute and chronic liver disease and can be also associated with cryoglobulinemia (SC). SC is a systemic vasculitic disease, typically characterized by lower extremity purpure, arthralgias and fatigue and by circulating immune complexes which precipitate at low temperatures. We examined the prevalence of SC in a prospective study of 84 patients with chronic HCV hepatitis. Cryoglobulinemia was detected in 44 patients (53.4%) and was associated with the severity of liver damage and the duration of the disease. The analysis of HCV genotypes demonstrated a prevalence of 1 b. The amount of cryoglobulinemia was low in all the patients with SC and only 20% showed a clinical syndrome.     

Association of human leucocyte antigen Class I (HLA-A and HLA-B) with chronic hepatitis C virus infection in Egyptian patients

Egypt has the highest prevalence of hepatitis C virus (HCV) in the world, ranging from 6% to 28% with an average of approximately 13.8% in the general population. It has been reported that human leucocyte antigen (HLA) alleles are associated with the outcome of HCV infection, but this associations showed ethnic and geographical differences. The objective of this study is to investigate the association between the frequencies of HLA Class I and chronic HCV infection in Egyptian patients and to find out whether there is a relation between certain HLA Class I antigens and HCV viral load, degree of fibrosis, activity and alanine aminotransferase (ALT) level. A case control study was conducted on 100 patients with chronic HCV infection and 150 healthy controls. HLA-A and HLA-B typing by complement-dependent micro-lympho-cytotoxicity assay was performed for both groups. HLA-A11 antigen was significantly increased in patients with chronic HCV infection versus controls (OR 3.98; 95% CI = 1.85-8.89; P = 0.001; and Pc = 0.021). HLA-B12, HLA-B13, HLA-B17 and HLA-B40 were higher in patients, and HLA-A32 and HLA-B14 were higher in controls, although the significance was lost after correction for multiple testing. HLA-A9 was significantly associated with low viral load (P = 0.008, Pc = 0.048). The results of this work implicate that HLA-A11 antigen may influence chronic HCV infection and may play a role in viral persistence. Different HLA Class I antigens are not associated with degree of liver fibrosis, grades of activity or level of ALT. However, HLA-A9 is associated with low HCV viral load in chronic HCV Egyptian patients.     

Associations between genes for killer immunoglobulin-like receptors and their ligands in patients with epithelial ovarian cancer

Killer immunoglobulin-like receptors (KIRs) regulate function of NK cells and subsets of T cells. HLA class I molecules are ligands for inhibitory KIRs while specificity of activating KIRs is mainly unknown. Both KIR and HLA genotypes are highly polymorphic.     

Association of NKG2A with treatment for chronic hepatitis C virus infection

Natural killer (NK) cells are critical to the immune response to viral infections. Their functions are controlled by receptors for major histocompatibility complex (MHC) class I, including NKG2A and killer‐cell immunoglobulin‐like receptors (KIR). In order to evaluate the role of MHC class I receptors in the immune response to hepatitis C virus infection we have studied patients with chronic HCV infection by multi‐parameter flow cytometry directly ex vivo. This has permitted evaluation of combinatorial expression of activating and inhibitory receptors on single NK cells. Individuals with chronic HCV infection had fewer CD56^dim NK cells than healthy controls (4·9 ± 3·4% versus 9·0 ± 5·9%, P < 0·05). Expression levels of the inhibitory receptor NKG2A was up‐regulated on NK cells from individuals with chronic hepatitis C virus (HCV) (NKG2A mean fluorescence intensity 5692 ± 2032 versus 4525 ± 1646, P < 0·05). Twelve individuals were treated with pegylated interferon and ribavirin. This resulted in a down‐regulation of NKG2A expression on CD56^dim NK cells. Individuals with a sustained virological response (SVR) had greater numbers of NKG2A‐positive, KIR‐negative NK cells than those without SVR (27·6 ± 9·6% NK cells versus 17·6 ± 5·7, P < 0·02). Our data show that NKG2A expression is dysregulated in chronic HCV infection and that NKG2A‐positive NK cells are associated with a beneficial response to pegylated interferon and ribavirin therapy.     

Natural killer cells in hepatitis C virus infection

Hepatitis C virus (HCV) infection induces the long-term risk of liver cirrhosis or hepatocellular carcinoma and in adults represents the most common cause of liver transplantation. Natural killer (NK) cells participate in innate immune responses with efficient direct antitumor and antiviral defense. Over the years, their complex interaction with downstream adaptive responses and with the regulation of immune responses has been increasingly recognized. Considerable advances have been made particularly in understanding the role of NK cells in the pathophysiology of HCV infection and their possible use as biological markers for clinical purposes. This review summarizes the available data on the role of NK cells in the natural history of HCV infection and their role in the outcome of treatment. The main objective of this review is to summarize recent advancements in the basic understanding of NK cell function highlighting their possible translational use in clinical practice. An integrated practical view on the possible use of currently available predictive immunogenetic and NK cell functional tests is provided, to support clinical management choices for optimal treatment of patients with both standard and new drug regimens.     

慢性粒细胞白血病患者杀伤细胞免疫球蛋白样受体(KIR)基因研究

目的探索CML患者的KIR（killer cell immunoglobulin-like receptors）基因的多态性与正常人群是否存在差异。方法应用PCR-SSP技术进行KIR基因的检测。结果共检出目前已知的18个KIR基因,在检测的全部个体中,3DL3,3DL2及2DL4出现频率均为100%。在CML的研究中发现KIR2DL1基因频率（0.509）比正常对照组（1.000）显著降低,KIR2DL1与CML呈现强负相关P〈0.001,与CML负相关的KIR基因尚有3DS1,2DL5和3DL1,P值分别等于0.021,0.029,0.031。其他KIR基因位点频率未发现统计学差异。结论CML患者具有其独特KIR基因位点频率的特点。     

Structure of killer cell immunoglobulin-like receptors and their recognition of the class I MHC molecules

Summary: The recognition of class I MHC molecules by killer cell immunoglobulin-like receptors (KIR) constitutes an integral part of immune surveillance by the innate immune system. To understand the molecular basis of this recognition, the structures of several members of this superfamily have been determined. Despite their functional diversity, members of this superfamily share many conserved structural features. A central question is how these receptors recognize their ligands. The recent determination of the crystal structure of KIR2DL2 in complex with HLA-Cw3 has revealed the molecular mechanisms underpinning this interaction, which ultimately modulates the cytolytic activity of natural killer cells. While the recognition of MHC molecules by KIR is characterized by a number of unique features, some unexpected similarities with T-cell receptor recognition of MHC molecules are also observed. The detailed interactions between KIR2DL2 and HLA-Cw3 and their functional implications will be reviewed here.     

Frequency of killer cell immunoglobulin-like receptors (KIRs) in Korean patients with chronic HCV infection

Natural killer (NK) cells play an important role in innate immunity, especially in the response to viral infections, such as hepatitis C virus (HCV). Killer cell immunoglobulin-like receptors (KIRs) are the primary receptors of NK cells that mediate innate immunity. KIRs are also involved in acquired immunity, because some KIRs are expressed on the surface of certain subsets of T cells. In this study, the frequency of KIR genes, HLA-C allotypes, and combinations of KIR genes with their HLA-C ligands were evaluated in two different groups of the Korean population: controls and patients with chronic HCV infection. The study population consisted of 147 Korean patients with chronic HCV infection. The frequency of KIR2DS2 in patients with chronic HCV infection was 9.5% which was significantly lower than 19.5% of the control (P < 0.01). However, there were no significant differences in the frequency of other KIR genes, HLA-C allotypes or different combinations of KIR genes with their HLA-C ligands. This study can contribute to the further prospective study with a larger scale, suggesting the assumption that KIR2DS2 might aid in HCV clearance by enhancing both the innate and acquired immune responses of people in Korea.     

杀伤细胞免疫球蛋白样受体(KIR)基因多态性与系统性红斑狼疮的关联性研究

目的 探讨杀伤细胞免疫球蛋白样受体（KIR）基因多态性与系统性红斑狼疮（SLE）的关联性。方法 采用序列特异性引物聚合酶链反应（SSP-PCR）法，分析93例SLE患者和123例无血缘关系的健康对照K／R基因位点的多态性。结果 SLE病例组KIR2DS1（P〈0．001）、KIR2DL2（P〈0．001）基因的阳性率较随机对照组显著升高。具有2个或2个以上活化性基因个体在SLE组（80．7％）较对照组（66．7％）明显增多，差异具有统计学意义（P=0．025）。SLE患者狼疮肾炎与非狼疮肾炎组K／R基因分布频率比较差异无统计学意义。按发病年龄分组后，SLE患者中不同发病年龄组间K／R基因频率分布比较差异无统计学意义。结论 KIR2DS1、KIR2DL2基因频率升高可能与SLE发病相关。     

Association of chronic active hepatitis and HLA B35 in patients with hepatitis B virus

Fifty-one patients with chronic active hepatitis were typed for their HLA-A, B, C, and DR antigens. We observed a significant increase in the antigen frequency of HLA B35 in patients compared with controls.     

Genetic profiles of killer-cell immunoglobulin-like receptors and HLA ligands in Thai blood donors

Killer-cell immunoglobulin-like receptors (KIRs) play an important role in natural killer (NK) cell regulation. Interaction of KIRs with human leukocyte antigen (HLA) class I molecules can transmit signals to regulate the function of NK cells. In this study, the diversities of KIR genes and their ligands in 500 Thai blood donors were investigated. The coexistence of inhibitory KIRs (iKIR), activating KIRs (aKIR) and their ligands in the same individuals were also analyzed. Overall, 36 KIR genotypes were identified. The most common genotype was genotype AA1 (40.8%). All individuals carried at least one iKIR-HLA pair whereas 18% of the individuals lacked aKIR-HLA pair. The most common compound KIR-HLA profile was the presence of 3 iKIR-HLA pairs with 1 aKIR-HLA pair (21.4%). The most common compound gene profile of KIR-HLA pairs was the combined presence of KIR2DL3-C1, 3DL1-Bw4, 3DL2-A3/A11 and the full length KIR2DS4-its ligands (8%). This study provided a comprehensive analysis of the KIR-HLA profiles in Thai blood donors in regards to KIR genotypes, HLA ligands, KIR-HLA ligand pairs and compound gene profiles of both iKIRs and aKIRs and their ligands. These findings will be useful as baseline information for further studies in the associations of KIR genes and various diseases.     

Killer cell immunoglobulin-like receptors and response to antiviral treatment in Thai patients with chronic hepatitis C virus genotype 3a

Genetic factors of the host have been shown to influence the outcome of treatment for hepatitis C virus (HCV) infection. Killer cell immunoglobulin‐like receptors (KIR) regulate natural killer (NK) cell activity by interaction with specific human leukocyte antigen (HLA) class I. In this study, KIR gene polymorphisms and their HLA ligands were investigated in 110 Thai patients with chronic HCV genotype 3a. Seventy‐six patients were sustained virological responders and 34 patients were virological non‐responders. KIR typing and HLA‐C typing were performed using PCR‐SSP (polymerase chain reaction with sequence specific primer). The frequency of HLA‐C1C2 was significantly higher in sustained responders than in non‐responders (P = 0.04). However, the frequencies of KIR2DL2/2DL3 genotype and KIR2DL2/2DL3‐HLA‐C1C1 genotype were significantly higher in non‐responders than in sustained responders (P = 0.02, 0.004, respectively). In summary, this study showed the association of KIR genes and ligands with the outcome of antiviral treatment in chronic hepatic C virus genotype 3a infection. J. Med. Virol. 83:1733–1737, 2011. © 2011 Wiley‐Liss, Inc.     

KIR genes and their human leukocyte antigen ligands in the progression to cirrhosis in patients with chronic hepatitis C

Natural killer (NK) cells play pivotal roles in immune responses against infection with viruses, such as hepatitis C virus (HCV), and killer cell immunoglobulin-like receptors (KIRs) are related to the activation and inhibition of NK cells. The aim of this study was to investigate the possibility that KIR genes and their human leukocyte antigen (HLA) ligands influence progression to cirrhosis in patients infected with genotype 1 of HCV. A total of 145 Brazilian patients with confirmed chronic hepatitis C grouped from F0 to F4 according to fibrosis progression to cirrhosis were evaluated. Genotyping of KIR and HLA genes was performed by polymerase chain reaction with sequence-specific oligonucleotide probes. The HLA-C2 KIR ligand was more frequent in patients than in healthy controls (74.5% vs 64.3%, p = 0.04, odds ratio (OR) = 1.6, 95% confidence interval (CI) = 1.03-2.52). Moreover, the HLA-C1C2 genotype was more frequent in patients with advanced fibrosis or cirrhosis (F3-F4 group) than in patients in the F0-F2 group (61.6% vs 44.7%, p = 0.06) and in the F4 group compared with the F0-F3 group (65.7% vs 46.7%, p = 0.05, OR = 2.19, 95% CI = 1.01-4.73). NK and KIR ligands may contribute to the development of liver damage in patients chronically infected by HCV.     

Concurrent hepatitis C virus and hepatitis delta virus superinfection in patients with chronic hepatitis B virus infection.

Since hepatitis C virus (HCV) and hepatitis delta virus (HDV) are transmitted by the same routes as hepatitis B virus (HBV), simultaneous or concurrent HCV and HDV infection in patients with chronic HBV infection may occur. To test this hypothesis and to examine the clinicohistological and immunopathological presentations of such multiple hepatitis virus infections, acute and/or convalescent serum specimens from 86 patients with acute HDV superinfection were tested by enzyme immunoassay for antibodies to HCV. Of the 86 patients, 18 (20.9%) were associated with HCV infection. Although patients with early mortality cannot be evaluated by the HCV markers used in this study, the results showed that the clinical and histologic features were similar except that patients with HCV infection were older than those without HCV infection (P less than 0.01). Immunopathological studies carried out within 2 months after the onset of acute HDV superinfection demonstrated that hepatitis B core antigen (HBcAg) was not detected in any patient and HDV antigen was detected in 18.2% of the patients with HCV infection whereas HBcAg and HDAg were found in 7% and 65.1%, respectively, of those without HCV coinfection (P less than 0.02). It is concluded that concurrent HCV and HDV superinfections can and do occur in patients with chronic HBV infection. In these triple viral infections, HCV may even transiently suppress HDV and HBV.     

Paired immunoglobulin-like receptors and their MHC class I recognition

The immunoglobulin-like receptors provide positive and negative regulation of immune cells upon recognition of various ligands, thus enabling those cells to respond properly to extrinsic stimuli. Murine paired immunoglobulin-like receptor (PIR)-A and PIR-B, a typical receptor pair of the immunoglobulin-like receptor family, are expressed on a wide range of cells in the immune system, such as B cells, mast cells, macrophages and dendritic cells, mostly in a pair-wise fashion. The PIR-A requires the homodimeric Fc receptor common gamma chain for its efficient cell-surface expression and for the delivery of an activation signal. In contrast, PIR-B inhibits receptor-mediated activation signals in vitro upon engagement with other activating-type receptors, such as the antigen receptor on B cells and the high-affinity Fc receptor for immunoglobulin E on mast cells. Recent identification of major histocompatibility complex (MHC) class I molecules as the physiological ligands for PIR has enabled us to attribute various immunological phenotypes observed in PIR-B-deficient mice to the consequences of the absence of a balanced interaction between PIR and MHC class I molecules expressed ubiquitously. Thus, PIR-A and PIR-B constitute a novel and physiologically important MHC class I recognition system.