Killer-cell Immunoglobulin-like Receptors define a potent effector program in human γδ T cells.

Genetic Disparities in Killer Cell Immunoglobulin-Like Receptors (KIR) and MHC Class I in Bone Marrow Failure Syndromes

NK cell development in a human stem cell niche: KIR expression occurs independently of the presence of HLA class I ligands

Objective. The genes for killer-cell immunoglobulin-like receptors (KIRs) have been cloned and their functions and expression in patients with rheumatoid arthritis (RA) have been partially clarified. However, the correlation between their expression and disease activity has not been analyzed in patients with RA. Thus, we measured KIR expression on lymphocytes in patients with RA, and assessed the correlation between KIR expression and disease activity. Patients and Methods. In the cross-sectional study, 15 patients (9 females and 6 males) who fulfilled the diagnostic criteria for RA were assessed. In the longitudinal study, patients who were followed-up for 3 months were assessed. CD158a/b expression on peripheral blood mononuclear cells (PBMC) of RA patients was analyzed using flow cytometry. Results. No significant correlation between KIR expression and CRP, ESR, or IgM-RF was observed. There was no remarkable change in the expression of KIRs between the baseline and after 3 months. Additionally, in the 5 patients whose expression of KIRs particularly changed, the time-related changes in the expression of KIRs were independent from those of inflammation parameters and IgM-RF. Conclusion. There was no correlation between KIR expression and disease activity; therefore, the clinical use of KIR expression should be limited, while unnatural KIR expression may be involved in the pathogenesis of RA, but not a recruitment of chronic inflammation to induce joint damage.

CD8 T cells express randomly selected KIRs with distinct specificities compared with NK cells

To exploit autologous NK cells for cancer immunotherapy, it is highly relevant to circumvent killer cell immunoglobulin-like receptor (KIR)-mediated self-inhibition of human NK cells by HLA-I-expressing tumor cells. Here, we show that stimulation of NK cells with IL-12/15/18 for two days led to downregulation of surface expression of the inhibitory KIR2DL2/L3, KIR2DL1 and KIR3DL1 receptors on peripheral blood NK cells. Downregulation of KIR expression was attributed to decreased KIR mRNA levels which could be re-induced already 3 days after re-culture in IL-2. Reduced KIR2DL2/L3 expression on IL-12/15/18-activated NK cells resulted in less inhibition upon antibody-mediated KIR engagement and increased CD16-dependent cytotoxicity in redirected lysis assays. Most importantly, downregulated KIR2DL2/L3 expression enabled enhanced cytotoxicity of IL-12/15/18-stimulated NK cells against tumor cells expressing cognate HLA-I molecules. NK cells pre-activated with IL-12/15/18 were previously shown to exert potent anti-tumor activity and memory-like long-lived functionality, mediating remission in a subset of acute myeloid leukemia (AML) patients in a clinical trial. Our study reveals a novel mechanism of IL-12/15/18 in improving the cytotoxicity of NK cells by reducing their sensitivity to inhibition by self-HLA-I due to decreased KIR expression, highlighting the potency of IL-12/15/18-activated NK cells for anti-tumor immunotherapy protocols.

Study question Is there a link between killer cell immunoglobulin-like receptors (KIRs) genes, haplotypes, or genotypes and recurrent implantation failure (RIF)? Summary answer The KIRAA1 genotype significantly increases the risk of RIF. The presence of the full-length receptor KIR2DS4norm in KIRAA haplotype patients is indicative of RIF development. What is known already KIRs are expressed by a subset of uterine natural killer cells (uNK cells). The KIRs family consists of 16 genes with high polymorphism that are divided into two main haplotypes: KIRAA and KIRBx. The KIRAA haplotype consists mostly of inhibitory KIRs and only one activating receptor, KIR2DS4, whose function is uncertain, whereas the Bx haplotype has a diverse gene composition, with a focus on activating receptor genes. The primary difference is in the balance of KIRs, which can activate or inhibit uNKcells’ ability to produce components required for embryo-implantation, and hence they are thought to being implicated in RIF. Study design, size, duration A three-year observational cohort research was conducted at a private infertility centre. A total of 82 patients were genotyped for activating or inhibiting KIR genes. The study included 60 ovarian normo-responders under the age of 40, with 28 women with repeated implantation failure serving as the study group and 32 as controls. Participants/materials, setting, methods DNA was extracted from blood samples of all participants, including RIF patients and controls. The 16 KIR genes were investigated utilizing PCR with Sequence-Specific Primer (SSP) technique. Individual KIR gene profiles, KIRAA and KIRBx haplotypes, and their unique genotypes were detected by software analyses of the collected data based on the reaction pattern when compared to patterns associated with described KIR gene sequences. All data were statistically analysed with the Fisher Exact Test. Main results and the role of chance The frequencies of the two main haplotypes, KIR AA and KIR Bx, were 28% and 72%, respectively. Patients with more inhibitory KIR genes (haplotype KIR AA) had a higher rate of RIF (60% vs 40% in controls; P = 0.2) than those with KIR Bx phenotypes (37.5% RIF vs 62.5% controls; p = 0.026). Further analysis of KIR AA revealed two genotypes: KIR AA 1 (31.82%) and KIR AA195 (68.18%). The KIR2DS4 locus in the full-length receptor (KIR2DS4-norm) was only expressed in KIR AA1. The distribution of RIF occurrences in the two different genotypes demonstrates a significant increase in the number of RIF in the possessors of KIR AA1 (75% vs 15%, p = 0.01), with no significant difference between the two groups in the KIR AA195. Limitations, reasons for caution The study encompasses small samples but the association strength was noticeably high, which confers the findings more confidence. Wider implications of the findings These findings imply that women with a high proportion of inhibited KIR genes (haplotype KIR AA) and KIR2DS4norm are more likely to develop RIF. Trial registration number NA

Shaping natural killer (NK) cell functions in human immunity and reproduction are diverse killer cell immunoglobulin-like receptors (KIRs) that recognize polymorphic MHC class I determinants. A survey of placental mammals suggests that KIRs serve as variable NK cell receptors only in certain primates and artiodactyls. Divergence of the functional and variable KIRs in primates and artiodactyls predates placental reproduction. Among artiodactyls, cattle but not pigs have diverse KIRs. Catarrhine (humans, apes, and Old World monkeys) and platyrrhine (New World monkeys) primates, but not prosimians, have diverse KIRs. Platyrrhine and catarrhine systems of KIR and MHC class I are highly diverged, but within the catarrhines, a stepwise co-evolution of MHC class I and KIR is discerned. In Old World monkeys, diversification focuses on MHC-A and MHC-B and their cognate lineage II KIR. With evolution of C1-bearing MHC-C from MHC-B, as informed by orangutan, the focus changes to MHC-C and its cognate lineage III KIR. Evolution of C2 from C1 and fixation of MHC-C drove further elaboration of MHC-C-specific KIR, as exemplified by chimpanzee. In humans, the evolutionary trajectory changes again. Emerging from reorganization of the KIR locus and selective attenuation of KIR avidity for MHC class I are the functionally distinctive KIR A and KIR B haplotypes.

Education of human natural killer cells by activating killer cell immunoglobulin-like receptors

The antibody-dependent cellular cytotoxicity (ADCC) effector function of natural killer (NK) cells is one of the known mechanisms of action for rituximab-based anti-cancer immunotherapy. Inhibition of the ADCC function of NK cells through interactions between inhibitory killer cell immunoglobulin-like receptors (KIRs) and HLA class I ligands is associated with resistance of cancers to rituximab. In this study, we deeply investigated the impact of KIR, HLA class I, and CD16 genotypes on rituximab-dependent NK cell responses in both an in vitro cellular model from healthy blood donors and ex vivo rituximab-treated non-Hodgkin lymphoma (NHL) patients. We highlight that an HLA environment with limited KIR ligands is beneficial to promoting a higher frequency of KIR+ NK cells including both educated and uneducated NK cells, two NK cell compartments that demonstrate higher rituximab-dependent degranulation than KIR− NK cells. In contrast, a substantial KIR ligand environment favors a higher frequency of poorly effective KIR− NK cells and numerous functional KIR/HLA inhibitions of educated KIR+ NK cells. These phenomena explain why NHL patients with limited KIR ligands respond better to rituximab. In this HLA environment, CD16 polymorphism appears to have a collateral effect. Furthermore, we show the synergic effect of KIR2DS1, which strongly potentiates NK cell ADCC from C2− blood donors against C2+ target cells. Taken together, these results pave the way for stronger prediction of rituximab responses for NHL patients. HLA class I typing and peripheral blood KIR+ NK cell frequency could be simple and useful markers for predicting rituximab response.

Natural killer (NK) cells have diverse roles in hominid immunity and reproduction. Modulating these functions are the interactions between major histocompatibility complex (MHC) class I molecules that are ligands for two NK cell surface receptor types. Diverse killer cell immunoglobulin-like receptors (KIR) bind specific motifs encoded within the polymorphic MHC class I cell surface glycoproteins, while, in more conserved interactions, CD94:NKG2A receptors recognize MHC-E with bound peptides derived from MHC class I leader sequences. The hominid lineage presents a choreographed co-evolution of KIR with their MHC class I ligands. MHC-A, -B, and -C are present in all great apes with species-specific haplotypic variation in gene content. The Bw4 epitope recognized by lineage II KIR is restricted to MHC-B but also present on some gorilla and human MHC-A. Common to great apes, but rare in humans, are MHC-B possessing a C1 epitope recognized by lineage III KIR. MHC-C arose from duplication of MHC-B and is fixed in all great apes except orangutan, where it exists on approximately 50% of haplotypes and all allotypes are C1-bearing. Recent study showed that gorillas possess yet another intermediate MHC organization compared to humans. Like orangutans, but unlike the Pan-Homo species, duplication of MHC-B occurred. However, MHC-C is fixed, and the MHC-C C2 epitope (absent in orangutans) emerges. The evolution of MHC-C drove expansion of its cognate lineage III KIR. Recently, position −21 of the MHC-B leader sequence has been shown to be critical in determining NK cell educational outcome. In humans, methionine (−21M) results in CD94:NKG2A-focused education whereas threonine (−21T) produces KIR-focused education. This is another dynamic position among hominids. Orangutans have exclusively −21M, consistent with their intermediate stage in lineage III KIR-focused evolution. Gorillas have both −21M and −21T, like humans, but they are unequally encoded by their duplicated B genes. Chimpanzees have near-fixed −21T, indicative of KIR-focused NK education. Harmonious with this observation, chimpanzee KIR exhibit strong binding and, compared to humans, smaller differences between binding levels of activating and inhibitory KIR. Consistent between these MHC-NK cell receptor systems over the course of hominid evolution is the evolution of polymorphism favoring the more novel and dynamic KIR system.

Introduction Malaria remains a leading cause of morbidity and mortality among children in sub-Saharan Africa, with Plasmodium falciparum infections manifesting either as asymptomatic or symptomatic disease. Natural killer (NK) cells are increasingly recognized as important contributors to malaria immunity, yet their role in mediating protection in children remains poorly understood. Methods This study aimed to characterize NK cell phenotypes and functions in children with symptomatic or asymptomatic malaria living in a transmission setting in Eastern Uganda. Peripheral blood mononuclear cell (PBMC) samples from 10 children enrolled in the MUSICAL study at symptomatic and asymptomatic timepoints; baseline, day 0 and day 14 were utilized for immunophenotyping and functional assays stimulated with IL-12, IL-15 and IL-18 and analysed using flow cytometry. NK cell subsets were defined as CD56bri, CD56dim and CD56neg, and further profiled for expression of adaptive markers (CD85j, CD57, NKG2C, LAG3, Siglec-7) and Killer-cell Immunoglobulin-like receptors (KIRs). Statistical comparisons were made using Wilcoxon signed rank test. Results CD56 NK cells were the most abundant subset across infection states, while CD56neg NK cells expanded at infection and were enriched in asymptomatic cases. Adaptive markers such as CD85j were highly expressed on CD56neg, whereas NKG2C and CD57 predominated CD56dim NK cells. Cytokine profiling revealed that CD56bri NK cells were the main producers of IFN-y, TNF and IL-10, particularly in symptomatic infections on day 0. KIR expression was relatively stable but KIR2DL2/L3/S2 was enriched on CD56dim and CD56neg. Conclusion These findings suggest that repeated malaria exposure drives NK cell differentiation and expansion of adaptive-like CD56neg, which may contribute to clinical tolerance. The duo pro- and anti-inflammatory cytokine responses highlight NK cells as both regulators and effectors of malaria immunity. This study provides novel insights into inmate immune adaptation in malaria and identifies NK cell subsets and markers that could inform vaccine development and biomarker discovery.

The immune system plays an important role in the control and elimination of malignant cells.In recent years, immunotherapy for treating tumors has received much attention due to its remarkable effects.There are currently two approaches to lead the field: programmed cell death protein-1/programmed death ligand-1 (PD-1/PD-L1) monoclonal antibody and killer cell immunoglobulin-like receptor (KIR)monoclonal antibody.It has been reported that PD-1/PD-L1 monoclonal antibody can reverse the inhibitory effect of activating T cells to kill tumor cells and thus exert a significant clinical response in patients with hematological tumors. KIR monoclonal antibody enhance the anti-tumor response of natural killer (NK) cells.It is a promising therapeutic strategy to mobilize both T cell and NK cell immune effector cells by PD-1/PD-L1 monoclonal antibody and KIR monoclonal antibody to produce synergistic anti-tumor response.This article intends to review the application of two antibodies in hemotological neoplasms. Key words: Immunotherapy; Suppressor factors, immunologic; Cell death; Receptors, natural killer cell; Hematologic neoplasms

The Yin and Yang of HLA and KIR in human disease

Research into the effects of host genetics on HIV disease susceptibility and progression, and on the efficacy and toxicity of drug treatment, occupies a particular position in the landscape of HIV research...

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