Genetic control of human NK cell repertoire

The role and novel use of natural killer cells in graft-versus-leukemia reactions after allogeneic transplantation

Allogeneic hematopoietic cell transplantation (HCT) has transformed over the past several decades through enhanced supportive care, reduced intensity conditioning (RIC), improved human leukocyte antigen (HLA) typing, and novel graft-versus-host disease (GVHD)-prevention and treatment strategies. Most notably, the implementation of post-transplantation cyclophosphamide (PTCy) has dramatically increased the safety and availability of this life-saving therapy. Given reductions in nonrelapse mortality (NRM) with these advances, the HCT community has placed even greater emphasis on developing ways to reduce relapse - the leading cause of death after HCT. When using RIC HCT, protection from relapse relies predominantly on graft-versus-leukemia (GVL) reactions. Donor lymphocyte infusion (DLI), adoptive cellular therapy, checkpoint inhibition, and post-HCT maintenance strategies represent approaches under study that aim to augment or synergize with the GVL effects of HCT. Optimizing donor selection algorithms to leverage GVL represents another active area of research. Many of these strategies seek to harness the effects of T cells, which for decades were felt to be the primary mediators of GVL and the focus of investigation in relapse reduction. However, there is growing interest in capitalizing on the ability of natural killer (NK) cells to yield potent anti-tumor effects. A potential advantage of NK cell-based approaches over T cell-mediated is the potential to reduce NRM in addition to relapse. By decreasing infection, without increasing the risk of GVHD, NK cells may mitigate NRM, while still yielding relapse reduction through identification and clearance of cancer cells. Most T cell-focused relapse-prevention strategies must weigh the benefits of relapse reduction against the increased risk of NRM from GVHD. In contrast, NK cells have the potential to reduce both, potentially tipping the scales significantly in favor of survival. Here, we will review the role of NK cells in GVL, optimization of NK cell match or mismatch, and burgeoning areas of research in NK cell therapy such as adoptive transfer and chimeric antigen receptor (CAR) NK cells.

HLA-F and LILRB1 Genetic Polymorphisms Associated with Alloimmunisation in Sickle Cell Disease

Red blood cell (RBC) transfusion remains a critical component in caring for the acute and chronic complications of sickle cell disease (SCD). Patient alloimmunisation is the main limitation of transfusion, which can worsen anaemia and lead to delayed haemolytic transfusion reaction or transfusion deadlock. Although biological risk factors have been identified for immunisation, patient alloimmunisation remains difficult to predict. We aimed to characterise genetic alloimmunisation factors to optimise the management of blood products compatible with extended antigen matching to ensure the self-sufficiency of labile blood products. Considering alloimmunisation in other clinical settings, like pregnancy and transplantation, many studies have shown that HLA Ib molecules (HLA-G, -E, and -F) are involved in tolerance mechanism; these molecules are ligands of immune effector cell receptors (LILRB1, LILRB2, and KIR3DS1). Genetic polymorphisms of these ligands and receptors have been linked to their expression levels and their influence on inflammatory and immune response modulation. Our hypothesis was that polymorphisms of HLA Ib genes and of their receptors are associated with alloimmunisation susceptibility in SCD patients. The alloimmunisation profile of thirty-seven adult SCD patients was analysed according to these genetic polymorphisms and transfusion history. Our results suggest that the alloimmunisation of SCD patients is linked to both HLA-F and LILRB1 genetic polymorphisms located in their regulatory region and associated with their protein expression level.

Receptors of immune cells mediates recognition for tumors

Over the last few decades, the immune system has been steered toward eradication of cancer cells with the help of cancer immunotherapy. T cells, B cells, monocytes/macrophages, dendritic cells, T-reg cells, and natural killer (NK) cells are some of the numerous immune cell types that play a significant part in cancer cell detection and reduction of inflammation, and the antitumor response. Briefly stated, chimeric antigen receptors, adoptive transfer and immune checkpoint modulators are currently the subjects of research focus for successful immunotherapy-based treatments for a variety of cancers. This chapter discusses ongoing investigations on the mechanisms and recent developments by which receptors of immune cells especially that of lymphocytes and monocytes/macrophages regulate the detection of immune system leading to malignancies. We will also be looking into the treatment strategies based on these mechanisms.

The Role of NK Cells and Their Exosomes in Graft Versus Host Disease and Graft Versus Leukemia

Natural killer (NK) cells are one of the innate immune cells that play an important role in preventing and controlling tumors and viral diseases, but their role in hematopoietic stem cell transplantation (HCT) is not yet fully understood. However, according to some research, these cells can prevent infections and tumor relapse without causing graft versus host disease (GVHD). In addition to NK cells, several studies are about the anti-leukemia effects of NK cell-derived exosomes that can highlight their roles in graft-versus-leukemia (GVL). In this paper, we intend to investigate the results of various articles on the role of NK cells in allogeneic hematopoietic cell transplantation and also their exosomes in GVL. Also, we have discussed the antiviral effects of these cells in post-HCT cytomegalovirus infection.

Distribution of KIR Genes and Their HLA Ligands in Different Viral Infectious Diseases: Frequency Study in Sicilian Population

Natural killer (NK) cells play a role in defence against viral infections by killing infected cells or by producing cytokines and interacting with adaptive immune cells. Killer immunoglobulin-like receptors (KIRs) regulate the activation of NK cells through their interaction with human leucocyte antigens (HLA). Ninety-six Sicilian patients positive to Human Immunodeficiency Virus-1 (HIV) and ninety-two Sicilian patients positive to SARS-CoV-2 were genotyped for KIRs and their HLA ligands. We also included fifty-six Sicilian patients with chronic hepatitis B (CHB) already recruited in our previous study. The aim of this study was to compare the distribution of KIR-HLA genes/groups of these three different infected populations with healthy Sicilian donors from the literature. We showed that the inhibitory KIR3DL1 gene and the KIR3DL1/HLA-B Bw4 pairing were more prevalent in individual CHB. At the same time, the frequency of HLA-C2 was increased in CHB compared to other groups. In contrast, the HLA-C1 ligand seems to have no contribution to CHB progression whereas it was significantly higher in COVID-19 and HIV-positive than healthy controls. These results suggest that specific KIR-HLA combinations can predict the outcome/susceptibility of these viral infections and allows to plan successful customized therapeutic strategies.

Graft-Versus-Solid-Tumor Effect: From Hematopoietic Stem Cell Transplantation to Adoptive Cell Therapies

After allogeneic hematopoietic stem cell transplantation (HSCT), donor lymphocytes may contribute to the regression of hematological malignancies and select solid tumors, a phenomenon referred to as the graft-versus-tumor effect (GVT). However, this immunologic reaction is frequently limited by either poor specificity resulting in graft-versus-host disease or the frequency of tumor-specific T cells being too low to induce a complete and sustained anti-tumor response. Over the past 2 decades, it has become clear that the driver of GVT following allogeneic HSCT is T-cell-mediated recognition of antigens presented on tumor cells. With that regard, even though the excitement for using HSCT in solid tumors has declined, clinical trials of HSCT in solid tumors provided proof of concept and valuable insights leading to the discovery of tumor antigens and the development of targeted adoptive cell therapies for cancer. In this article, we review the results of clinical trials of allogeneic HSCT in solid tumors. We focus on lessons learned from correlative studies of these trials that hold the potential for the creation of tumor-specific immunotherapies with greater efficacy and safety for the treatment of malignancies.

HLA-C and KIR permutations influence chronic obstructive pulmonary disease risk

A role for hereditary influences in the susceptibility for chronic obstructive pulmonary disease (COPD) is widely recognized. Cytotoxic lymphocytes are implicated in COPD pathogenesis, and functions of these leukocytes are modulated by interactions between their killer cell Ig-like receptors (KIR) and human leukocyte antigen–Class I (HLA–Class I) molecules on target cells. We hypothesized HLA–Class I and KIR inheritance affect risks for COPD. HLA–Class I alleles and KIR genotypes were defined by candidate gene analyses in multiple cohorts of patients with COPD (total n = 392) and control smokers with normal spirometry (total n = 342). Compared with controls, patients with COPD had overrepresentations of HLA-C*07 and activating KIR2DS1, with underrepresentations of HLA-C*12. Particular HLA-KIR permutations were synergistic; e.g., the presence of HLA-C*07 + KIR2DS1 + HLA-C12^null versus HLAC*07^null + KIR2DS1^null + HLA-C12 was associated with COPD, especially among HLA-C1 allotype homozygotes. Cytotoxicity of COPD lymphocytes was more enhanced by KIR stimulation than those of controls and was correlated with lung function. These data show HLA-C and KIR polymorphisms strongly influence COPD susceptibility and highlight the importance of lymphocyte-mediated cytotoxicity in COPD pathogenesis. Findings here also indicate that HLA-KIR typing could stratify at-risk patients and raise possibilities that HLA-KIR axis modulation may have therapeutic potential.

Relapse Protection Following Early Cytomegalovirus Reactivation after Hematopoietic Stem Cell Transplantation Is Limited to HLA-C Killer Cell Immunoglobulin-Like Receptor Ligand Homozygous Recipients

Although the risk for nonrelapse mortality (NRM) associated with early cytomegalovirus (CMV) reactivation (CMVR) after allogeneic hematopoietic stem cell transplantation (HSCT) is well established, debate is ongoing on whether CMVR may reduce the risk of primary disease relapse. The aim of this study was to evaluate relapse protection following early CMV reactivation after HSCT in the context of the recipient HLA-C killer cell immunoglobulin-like receptor ligands (KIRLs). In this retrospective bicentric study, 406 matched related or unrelated donor transplantations for acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS) were stratified by HLA-C KIRL group (homozygous versus heterozygous) and analyzed separately for the impact of early CMVR on the cumulative incidences of relapse, NRM, and acute and chronic graft-versus-host-disease (GVHD) using landmark and multistate analyses. By landmark analysis of patients alive and relapse-free at 45 days post-HSCT, HLA-C KIRL homozygous recipients (C1/1 or C2/2) had a lower risk of subsequent relapse if CMVR occurred before this landmark (subhazard ratio [sHR], 0.36; P = .002). In contrast, in HLA-C KIRL heterozygous (C1/2) recipients, early CMVR had no impact on subsequent relapse (sHR, 0.88; P = .63). NRM (sHR, 3.31; P < .001) and grade III-IV acute GVHD (sHR, 2.60; P = .04) were significantly increased after early CMVR in the homozygous cohort, but not in the heterozygous cohort (NRM: sHR, 1.23; P = .53; grade III-IV acute GVHD: sHR, 1.40; P = .50). Multivariable landmark analyses and a multistate model confirmed the limitation of the relapse-protective effect of early CMVR to the homozygous cohort. Chronic GVHD and overall survival were not influenced in neither cohort. An antileukemic effect of early CMVR after HSCT for AML/MDS was significant but strictly limited to recipients homozygous for HLA-C KIRL. However, particularly in this cohort, CMVR had an adverse impact on aGVHD and NRM.

Cellular Therapy in Pediatric Hematologic Malignancies

Advances in cellular therapies for pediatric patients have created many opportunities for improved survival with reduced morbidity. This article reviews current cellular therapies in pediatric hematological malignancy, including the most updated practices in hematopoietic stem cell transplant and the use of chimeric antigen receptor (CAR) therapy in T cells. Hematopoietic stem cell transplant has evolved with improvements in chemotherapy regimens, immunosuppression, and donor-matching options. Novel therapies in development which will likely further improve the options for patients are reviewed including Natural Killer, Regulatory T-cells and αβ depletion.

The Genetic Mechanisms Driving Diversification of the KIR Gene Cluster in Primates

The activity and function of natural killer (NK) cells are modulated through the interactions of multiple receptor families, of which some recognize MHC class I molecules. The high level of MHC class I polymorphism requires their ligands either to interact with conserved epitopes, as is utilized by the NKG2A receptor family, or to co-evolve with the MHC class I allelic variation, which task is taken up by the killer cell immunoglobulin-like receptor (KIR) family. Multiple molecular mechanisms are responsible for the diversification of the KIR gene system, and include abundant chromosomal recombination, high mutation rates, alternative splicing, and variegated expression. The combination of these genetic mechanisms generates a compound array of diversity as is reflected by the contraction and expansion of KIR haplotypes, frequent birth of fusion genes, allelic polymorphism, structurally distinct isoforms, and variegated expression, which is in contrast to the mainly allelic nature of MHC class I polymorphism in humans. A comparison of the thoroughly studied human and macaque KIR gene repertoires demonstrates a similar evolutionarily conserved toolbox, through which selective forces drove and maintained the diversified nature of the KIR gene cluster. This hypothesis is further supported by the comparative genetics of KIR haplotypes and genes in other primate species. The complex nature of the KIR gene system has an impact upon the education, activity, and function of NK cells in coherence with an individual’s MHC class I repertoire and pathogenic encounters. Although selection operates on an individual, the continuous diversification of the KIR gene system in primates might protect populations against evolving pathogens.

The effect of KIR and HLA polymorphisms on dengue infection and disease severity in northeastern Thais

Killer cell immunoglobulin-like receptors (KIRs) are cell surface receptors on natural killer (NK) cells and subsets of T cells. The interaction between KIRs and their cognate ligands (Human leukocyte antigen class I molecules, HLA class I) modulates the immune response of NK cells, in particular through clearance of virus-infected cells. Here, we investigated the effect of KIRs and HLA ligands on dengue infections and disease severity. The KIRs and HLA ligands were identified in 235 healthy controls (HC) and 253 dengue patients (DEN) using polymerase chain reaction with sequence specific primer (PCR-SSP); moreover, DEN was classified to 100 dengue fever (DF) and 153 dengue haemorrhagic fever (DHF). Risks were expressed as odds ratios (ORs) and 95% confidence intervals (CIs) with significance set at a two-tailed P value of < 0.05. The Bonferroni correction was applied for multiple comparisons. Twelve significant associations were observed in dengue infections and disease severity; however, two outcomes survived after the Bonferroni correction. Of these, HLA-A11 was associated with an increased risk to develop dengue disease (OR 2.41, 95% CI 1.62-3.60, P^c = 0.004), while KIR3DS1⁺ Bw4 was a protective genotype to developing DHF (OR 0.28, 95% CI 0.16-0.48, P^c < 0.001). This study revealed an important role of KIR and HLA ligands in innate immune responses to dengue viral infections and, in particular, their effect on clinical outcomes and disease severity.

Natural killer cells: From surface receptors to the cure of high-risk leukemia (Ceppellini Lecture)

Natural killer (NK) cells are innate immune effector cells involved in the first line of defense against viral infections and malignancies. In the last three decades, the identification of HLA class I‐specific inhibitory killer immunoglobulin‐like receptors (KIR) and of the main activating receptors has strongly improved our understanding of the mechanisms regulating NK cell functions. The increased knowledge on how NK cells discriminate healthy cells from damaged cells has made it possible to transfer basic research notions to clinical applications. Of particular relevance is the strong NK‐mediated anti‐leukemia effect in haploidentical hematopoietic stem cell transplantation to cure high‐risk leukemia.

Association of Killer Cell Immunoglobulin-like Receptor Genotypes and Haplotypes in Dry Eye Disease Patients Treated with Restasis and Systane

Purpose: whether the Killer immunoglobulin-like receptor (KIR) genotypes and haplotypes are associated with the improvement in dry eye disease (DED) patients treated with Restasis and Systane (RS) remain unclear.Methods: Polymerase chain reaction with sequence-specific primers (PCR-SSP) was used to analyze KIR genes in a Chinese Han population of 198 severe DED patients treated with RS.Results: The higher frequencies of KIR genotype M, AF, AJ and haplotype 2 and 8 (P = .001, P = .03, P = .004, P = .000 and P = .023, respectively) and the lower frequencies of genotype AG and haplotype 1 (P = .000 and P = .000, respectively) were observed in complete responders (CR) than those in null or partial responders (NPR) of DED patients treated by RS.Conclusions: The patients with KIR genotype M, AF and AJ might be of advantage to therapy with RS, which are useful for improving novel personalized precise therapy strategy in DED patients.

Natural Killer Cells as Allogeneic Effectors in Adoptive Cancer Immunotherapy

Natural killer (NK) cells are attractive within adoptive transfer settings in cancer immunotherapy due to their potential for allogeneic use; their alloreactivity is enhanced under conditions of killer immunoglobulin-like receptor (KIR) mismatch with human leukocyte antigen (HLA) ligands on cancer cells. In addition to this, NK cells are platforms for genetic modification, and proliferate in vivo for a shorter time relative to T cells, limiting off-target activation. Current clinical studies have demonstrated the safety and efficacy of allogeneic NK cell adoptive transfer therapies as a means for treatment of hematologic malignancies and, to a lesser extent, solid tumors. However, challenges associated with sourcing allogeneic NK cells have given rise to controversy over the contribution of NK cells to graft-versus-host disease (GvHD). Specifically, blood-derived NK cell infusions contain contaminating T cells, whose activation with NK-stimulating cytokines has been known to lead to heightened release of proinflammatory cytokines and trigger the onset of GvHD in vivo. NK cells sourced from cell lines and stem cells lack contaminating T cells, but can also lack many phenotypic characteristics of mature NK cells. Here, we discuss the available published evidence for the varying roles of NK cells in GvHD and, more broadly, their use in allogeneic adoptive transfer settings to treat various cancers.

Role of Immunogenetics in the Outcome of HCMV Infection: Implications for Ageing

The outcome of host-virus interactions is determined by a number of factors, some related to the virus, others to the host, such as environmental factors and genetic factors. Therefore, different individuals vary in their relative susceptibility to infections. Human cytomegalovirus (HCMV) is an important pathogen from a clinical point of view, as it causes significant morbidity and mortality in immunosuppressed or immunosenescent individuals, such as the transplanted patients and the elderly, respectively. It is, therefore, important to understand the mechanisms of virus infection control. In this review, we discuss recent advances in the immunobiology of HCMV-host interactions, with particular emphasis on the immunogenetic aspects (human leukocyte antigens, HLA; killer cell immunoglobulin-like receptors, KIRs; immunoglobulin genetic markers, GM allotypes) to elucidate the mechanisms underlying the complex host-virus interaction that determine various outcomes of HCMV infection. The results, which show the role of humoral and cellular immunity in the control of infection by HCMV, would be valuable in directing efforts to reduce HCMV spurred health complications in the transplanted patients and in the elderly, including immunosenescence. In addition, concerning GM allotypes, it is intriguing that, in a Southern Italian population, alleles associated with the risk of developing HCMV symptomatic infection are negatively associated with longevity.

Association of KIR Genotypes and Haplotypes in HBeAg-positive Chronic Hepatitis B Patients Treated with Entecavir

BACKGROUND

A large proportion of patients with chronic hepatitis B (CHB) in China do not respond to entecavir (ETV) treatment. It remains unclear whether the Killer immunoglobulin-like receptor (KIR) genotypes and haplotypes were associated with the advantage of seroconversion in phepatitis B e-Antigen (HBeAg) positive CHB patients treated with ETV.

METHODS

Polymerase chain reaction with sequence-specific primers (PCR-SSP) was used to analyze KIR genes in a Chinese Han population of 198 ETV-treated HBeAg-positive CHB patients and 200 healthy controls. Of the 198 patients, 59 were complete response group (CRG) and 139 were null or partial response group (NPRG) to the treatment with ETV.

RESULTS

The frequencies of KIR genotype M, and haplotype 8 were significantly higher(P = 0.017, OR = 2.497，95%CI = 5.39-1.16 and P = 0.034, OR = 1.905，95%CI = 3.48-1.04, respectively), while the frequencies of genotype AH and haplotype 5 were significantly lower (P = 0.039, OR = 0.504, 95%CI = 0.97-0.26 and P = 0.031, OR = 0.601, 95%CI = 0.96-0.38, respectively) in HBeAg-positive CHB patient group than those in healthy group. Of note, the frequencies of KIR genotype AF and haplotype 1 were significantly higher (P = 0.022, OR = 2.860, 95%CI = 7.24-1.13 and P = 0.001, OR = 3.261, 95%CI = 6.47-1.64, respectively), while the frequencies of genotype AH and haplotype 5 were significantly lower (P = 0.038, OR = 0.338, 95%CI = 0.98-0.12 and P = 0.004, OR = 0.354, 95%CI = 0.73-0.17, respectively) in NPRG than those in CRG.

CONCLUSIONS

The patients with KIR genotype AF and haplotype 1 might be negative, while genotype AH and haplotype 5 might be of advantage to the therapy with ETV, which are useful for improving novel personalized precise therapy strategy in HBeAg-positive CHB patients.

Glioblastoma Stem-Like Cells Are More Susceptible Than Differentiated Cells to Natural Killer Cell Lysis Mediated Through Killer Immunoglobulin-Like Receptors-Human Leukocyte Antigen Ligand Mismatch and Activation Receptor-Ligand Interactions

Glioblastoma (GBM) is the most aggressive brain malignancy in adults, where survival is approximately 14.6 months. Novel therapies are urgently needed and immunotherapy has hailed a new dawn for treatment of solid tumors. Natural killer (NK) cells may be amenable therapeutic effectors against heterogeneous GBM, since they also do not require co-stimulation and antigen specificity. However, it is unclear how culture media routinely used in pre-clinical studies affect GBM cell responses to NK-mediated cytotoxicity. We hypothesized that the culture medium would affect GBM cell phenotype, proliferation, and responses to NK cytotoxicity. We investigated in paired analyses n = 6 patient-derived primary GBM cells propagated in stem cell or serum-containing medium for morphology, proliferation, as well as susceptibility to NK cytolysis and related this to expression of surface and intracellular lineage markers, as well as ligands for NK cell activating and inhibitory receptors. We genotyped the GBM cells for human leukocyte antigen (HLA) as well as the killer immunoglobulin-like receptors (KIR) of the n = 6 allogeneic NK cells used as effector cells. Culture in serum-containing medium induced a switch in GBM cell morphology from suspension neuropsheres to adherent epithelial-mesenchymal-like phenotypes, which was partially reversible. The differentiated cells diminished expression of nestin, CD133 (prominin-1), and A2B5 putative glioma stem-cell markers, attenuated growth, diminished expression of ligands for activating NK cell receptors, while upregulating class I HLA ligands for NK cell inhibitory receptors. When maintained in serum-containing medium, fewer GBM cells expressed intercellular cell adhesion molecule-1 (ICAM-1) and were less susceptible to lysis by NK cells expressing αLβ2 integrin receptor (LFA-1), mediated through combination of inhibitory KIR-HLA ligand mismatch and diminished activation receptor-ligand interactions compared to cells maintained in stem cell media. We conclude that development of preclinical immunotherapy strategies against GBM should not use cells propagated in serum-containing media to avoid misinterpretation of potential therapeutic responses.

NK cell therapy for hematologic malignancies

Natural killer (NK) cells are part of the innate immune system and represent the first line of defense against infections and tumors. In contrast to T cells, NK cells do not require prior antigen sensitization to induce cytotoxicity and do not cause graft-versus-host disease. These, along with other advantages, make NK cells an attractive candidate for adoptive cellular therapy. Herein, we describe the mechanisms of NK cell cytotoxicity, which is governed by an intricate balance between various activating and inhibitory receptors, including the killer cell immunoglobulin-like receptors (KIRs). We illustrate the advantages of NK alloreactivity as demonstrated in various types of hematopoietic stem cell transplants (HSCT), such as haploidentical, human leukocyte antigen-matched related or unrelated donor and umbilical cord blood transplant. We elaborate on different models used to predict NK cell alloreactivity in these studies, which are either based on the absence of the ligands for inhibitory KIRs, presence of activating NK cell receptors and KIR genes content in donors, or a combination of these. We will review clinical studies demonstrating anti-tumor efficacy of NK cells used either as a stand-alone immunotherapy or as an adjunct to HSCT and novel genetic engineering strategies to improve the anti-tumor activity of NK cells.

Association of maternal KIR gene content polymorphisms with reduction in perinatal transmission of HIV-1

The role of killer cell immunoglobulin-like receptors (KIRs) in the transmission of HIV-1 has not been extensively studied. Here, we investigated the association of KIR gene content polymorphisms with perinatal HIV-1 transmission. The KIR gene family comprising 16 genes was genotyped in 313 HIV-1 positive Kenyan mothers paired with their infants. Gene content polymorphisms were presented as presence of individual KIR genes, haplotypes, genotypes and KIR gene concordance. The genetic data were analyzed for associations with perinatal transmission of HIV. There was no association of infant KIR genes with perinatal HIV-1 transmission. After adjustment for gravidity, viral load, and CD4 cell count, there was evidence of an association between reduction in perinatal HIV-1 transmission and the maternal individual KIR genes KIR2DL2 (adjusted OR = 0.50; 95% CI: 0.24–1.02, P = 0.06), KIR2DL5 (adjusted OR = 0.47; 95% CI: 0.23–0.95, P = 0.04) and KIR2DS5 (adjusted OR = 0.39; 95% CI: 0.18–0.80, P = 0.01). Furthermore, these maternal KIR genes were only significantly associated with reduction in perinatal HIV transmission in women with CD4 cell count ≥ 350 cells/ μl and viral load <10000 copies/ml. Concordance analysis showed that when both mother and child had KIR2DS2, there was less likelihood of perinatal HIV-1 transmission (adjusted OR = 0.44; 95% CI: 0.20–0.96, P = 0.039). In conclusion, the maternal KIR genes KIR2DL2, KIR2DL5, KIR2DS5, and KIR2DS2 were associated with reduction of HIV-1 transmission from mother to child. Furthermore, maternal immune status is an important factor in the association of KIR with perinatal HIV transmission.

Restoring Natural Killer Cell Immunity against Multiple Myeloma in the Era of New Drugs

Transformed plasma cells in multiple myeloma (MM) are susceptible to natural killer (NK) cell-mediated killing via engagement of tumor ligands for NK activating receptors or “missing-self” recognition. Similar to other cancers, MM targets may elude NK cell immunosurveillance by reprogramming tumor microenvironment and editing cell surface antigen repertoire. Along disease continuum, these effects collectively result in a progressive decline of NK cell immunity, a phenomenon increasingly recognized as a critical determinant of MM progression. In recent years, unprecedented efforts in drug development and experimental research have brought about emergence of novel therapeutic interventions with the potential to override MM-induced NK cell immunosuppression. These NK-cell enhancing treatment strategies may be identified in two major groups: (1) immunomodulatory biologics and small molecules, namely, immune checkpoint inhibitors, therapeutic antibodies, lenalidomide, and indoleamine 2,3-dioxygenase inhibitors and (2) NK cell therapy, namely, adoptive transfer of unmanipulated and chimeric antigen receptor-engineered NK cells. Here, we summarize the mechanisms responsible for NK cell functional suppression in the context of cancer and, specifically, myeloma. Subsequently, contemporary strategies potentially able to reverse NK dysfunction in MM are discussed.

Natural killer cell-mediated immunosurveillance of human cancer

The contribution of natural killer (NK) cells to immunosurveillance of human cancer remains debatable. Here, we discuss advances in several areas of human NK cell research, many of which support the ability of NK cells to prevent cancer development and avoid relapse following adoptive immunotherapy. We describe the molecular basis for NK cell recognition of human tumor cells and provide evidence for NK cell-mediated killing of human primary tumor cells ex vivo. Subsequently, we highlight studies demonstrating the ability of NK cells to migrate to, and reside in, the human tumor microenvironment where selection of tumor escape variants from NK cells can occur. Indirect evidence for NK cell immunosurveillance against human malignancies is provided by the reduced incidence of cancer in individuals with high levels of NK cell cytotoxicity, and the significant clinical responses observed following infusion of human NK cells into cancer patients. Finally, we describe studies showing enhanced tumor progression, or increased cancer incidence, in patients with inherited and acquired defects in cellular cytotoxicity. All these observations have in common that they, either indirectly or directly, suggest a role for NK cells in mediating immunosurveillance against human cancer. This opens up for exciting possibilities with respect to further exploring NK cells in settings of adoptive immunotherapy in human cancer.

Killer Immunoglobulin-Like Receptor Allele Determination Using Next-Generation Sequencing Technology

The impact of natural killer (NK) cell alloreactivity on hematopoietic stem cell transplantation (HSCT) outcome is still debated due to the complexity of graft parameters, HLA class I environment, the nature of killer cell immunoglobulin-like receptor (KIR)/KIR ligand genetic combinations studied, and KIR⁺ NK cell repertoire size. KIR genes are known to be polymorphic in terms of gene content, copy number variation, and number of alleles. These allelic polymorphisms may impact both the phenotype and function of KIR⁺ NK cells. We, therefore, speculate that polymorphisms may alter donor KIR⁺ NK cell phenotype/function thus modulating post-HSCT KIR⁺ NK cell alloreactivity. To investigate KIR allele polymorphisms of all KIR genes, we developed a next-generation sequencing (NGS) technology on a MiSeq platform. To ensure the reliability and specificity of our method, genomic DNA from well-characterized cell lines were used; high-resolution KIR typing results obtained were then compared to those previously reported. Two different bioinformatic pipelines were used allowing the attribution of sequencing reads to specific KIR genes and the assignment of KIR alleles for each KIR gene. Our results demonstrated successful long-range KIR gene amplifications of all reference samples using intergenic KIR primers. The alignment of reads to the human genome reference (hg19) using BiRD pipeline or visualization of data using Profiler software demonstrated that all KIR genes were completely sequenced with a sufficient read depth (mean 317× for all loci) and a high percentage of mapping (mean 93% for all loci). Comparison of high-resolution KIR typing obtained to those published data using exome capture resulted in a reported concordance rate of 95% for centromeric and telomeric KIR genes. Overall, our results suggest that NGS can be used to investigate the broad KIR allelic polymorphism. Hence, these data improve our knowledge, not only on KIR⁺ NK cell alloreactivity in HSCT but also on the role of KIR⁺ NK cell populations in control of viral infections and diseases.

Improved full-length killer cell immunoglobulin-like receptor transcript discovery in Mauritian cynomolgus macaques

Killer cell immunoglobulin-like receptors (KIRs) modulate disease progression of pathogens including HIV, malaria, and hepatitis C. Cynomolgus and rhesus macaques are widely used as nonhuman primate models to study human pathogens, and so, considerable effort has been put into characterizing their KIR genetics. However, previous studies have relied on cDNA cloning and Sanger sequencing that lack the throughput of current sequencing platforms. In this study, we present a high throughput, full-length allele discovery method utilizing Pacific Biosciences circular consensus sequencing (CCS). We also describe a new approach to Macaque Exome Sequencing (MES) and the development of the Rhexome1.0, an adapted target capture reagent that includes macaque-specific capture probe sets. By using sequence reads generated by whole genome sequencing (WGS) and MES to inform primer design, we were able to increase the sensitivity of KIR allele discovery. We demonstrate this increased sensitivity by defining nine novel alleles within a cohort of Mauritian cynomolgus macaques (MCM), a geographically isolated population with restricted KIR genetics that was thought to be completely characterized. Finally, we describe an approach to genotyping KIRs directly from sequence reads generated using WGS/MES reads. The findings presented here expand our understanding of KIR genetics in MCM by associating new genes with all eight KIR haplotypes and demonstrating the existence of at least one KIR3DS gene associated with every haplotype.

Cancer treatment and the KIR-HLA system: an overview

Accumulating evidence indicates that the success of cancer therapy depends not only on a combination of adequate procedures (surgery, chemotherapy and radiotherapy) that aim to eliminate all tumor cells, but also on the functional state of the host immune system. HLA and KIR molecules, in particular, are critical to the interactions between tumor cells and both innate and adaptive immune cells such as NK cells and T cells. Different KIR-HLA gene combinations as well as different HLA expression levels on tumor cells associate with variable tumor prognosis and response to treatment. On the other hand, different therapies have different effects on HLA molecules and immune cell functions regulated by these molecules. Here, we provide an overview of the KIR-HLA system, a description of its alterations with clinical relevance in diverse tumor types, and an analysis of the consequences that conventional cancer therapies may have on it. We also discuss how this knowledge can be exploited to identify potential immunological biomarkers that can help to select patients for tailored therapy.

Reduction of Relapse after Unrelated Donor Stem Cell Transplantation by KIR-Based Graft Selection

Besides donor T cells, natural killer (NK) cells are considered to have a major role in preventing relapse after allogeneic hematopoietic stem cell transplantation (HSCT). After T-cell-depleted haploidentical HSCT, a strong NK alloreactivity has been described. These effects have been attributed to killer-cell immunoglobulin-like receptors (KIR). Abundant reports suggest a major role of KIR not only on outcome after haploidentical HSCT but also in the unrelated donor setting. In this review, we give a brief overview of the mechanism of NK cell activation, nomenclature of KIR haplotypes, human leukocyte antigen (HLA) groups, and distinct models for prediction of NK cell alloreactivity. It can be concluded that KIR-ligand mismatch seems to provoke adverse effects in unrelated donor HSCT with reduced overall survival and increased risk for high-grade acute graft-versus-host disease. The presence of activating KIR, as seen in KIR haplotype B, as well as the patient’s HLA C1/x haplotype might reduce relapse in myeloid malignancies.

NKG2A-Expressing Natural Killer Cells Dominate the Response to Autologous Lymphoblastoid Cells Infected with Epstein-Barr Virus

Epstein-Barr virus (EBV) is a human γ-herpesvirus that establishes latency and lifelong infection in host B cells while achieving a balance with the host immune response. When the immune system is perturbed through immunosuppression or immunodeficiency, however, these latently infected B cells can give rise to aggressive B cell lymphomas. Natural killer (NK) cells are regarded as critical in the early immune response to viral infection, but their role in controlling expansion of infected B cells is not understood. Here, we report that NK cells from healthy human donors display increased killing of autologous B lymphoblastoid cell lines (LCLs) harboring latent EBV compared to primary B cells. Coculture of NK cells with autologous EBV⁺ LCL identifies an NK cell population that produces IFNγ and mobilizes the cytotoxic granule protein CD107a. Multi-parameter flow cytometry and Boolean analysis reveal that these functional cells are enriched for expression of the NK cell receptor NKG2A. Further, NKG2A⁺ NK cells more efficiently lyse autologous LCL than do NKG2A^- NK cells. More specifically, NKG2A⁺2B4⁺CD16^-CD57^-NKG2C^-NKG2D⁺ cells constitute the predominant NK cell population that responds to latently infected autologous EBV⁺ B cells. Thus, a subset of NK cells is enhanced for the ability to recognize and eliminate autologous, EBV-infected transformed cells, laying the groundwork for harnessing this subset for therapeutic use in EBV⁺ malignancies.

Milestones of Hematopoietic Stem Cell Transplantation - From First Human Studies to Current Developments

Since the early beginnings, in the 1950s, hematopoietic stem cell transplantation (HSCT) has become an established curative treatment for an increasing number of patients with life-threatening hematological, oncological, hereditary, and immunological diseases. This has become possible due to worldwide efforts of preclinical and clinical research focusing on issues of transplant immunology, reduction of transplant-associated morbidity, and mortality and efficient malignant disease eradication. The latter has been accomplished by potent graft-versus-leukemia (GvL) effector cells contained in the stem cell graft. Exciting insights into the genetics of the human leukocyte antigen (HLA) system allowed improved donor selection, including HLA-identical related and unrelated donors. Besides bone marrow, other stem cell sources like granulocyte-colony stimulating-mobilized peripheral blood stem cells and cord blood stem cells have been established in clinical routine. Use of reduced-intensity or non-myeloablative conditioning regimens has been associated with a marked reduction of non-hematological toxicities and eventually, non-relapse mortality allowing older patients and individuals with comorbidities to undergo allogeneic HSCT and to benefit from GvL or antitumor effects. Whereas in the early years, malignant disease eradication by high-dose chemotherapy or radiotherapy was the ultimate goal; nowadays, allogeneic HSCT has been recognized as cellular immunotherapy relying prominently on immune mechanisms and to a lesser extent on non-specific direct cellular toxicity. This chapter will summarize the key milestones of HSCT and introduce current developments.

Killer-cell immunoglobulin-like receptors and cytomegalovirus reactivation during late pregnancy

Human cytomegalovirus (CMV) represents an important public health concern as it is associated with severe morbidity and mortality in transplant recipients, HIV-infected individuals and pregnant women given the risk of congenital infection. Congenital CMV is a leading cause of neurological sequelae, developmental delay and birth defects worldwide. Cytomegalovirus can be transmitted to the foetus following maternal infection or reactivation. NK cells expressing killer-cell immunoglobulin-like receptors (KIR) are part of the innate immune system and the first line of defence against viral incursions. Previous reports have shown that KIR genes are associated with CMV infections in the post-transplant setting. In this study, we set out to determine whether a protective effect of KIR genes over CMV infection is seen in Mexican pregnant women. Cytomegalovirus infection was assessed through nucleic acid testing in 200 pregnant women and 600 healthy blood donors comprising the Mexican mestizo reference population. Killer-cell immunoglobulin-like receptors and HLA-C genotypes were obtained from 200 pregnant women and 300 reference samples using a comprehensive PCR-SSP approach. We observed statistically lower carrier frequencies of cB03|tA01 gene-content haplotype, of cB03 haplotype motif, of the KIR2DL5 + 2DS3/2DS5 gene pair and of KIR2DL5 amongst CMV-positive pregnant women in comparison with those CMV negative. None of these were associated with CMV status in the reference population. Logistic regression analysis revealed that the most important factor determining CMV status during third-trimester pregnancies was the KIR2DL5 + 2DS3/2DS5 gene pair (OR 0.376 (95%CI 0.174, 0.811, P = 0.013). Our results indicate that CMV-protective KIR gene associations described in Caucasoid populations are also present in the genetically distinct Mexican mestizo population. Our results suggest that certain KIR gene combinations provide protection against CMV infections occurring during late-term pregnancies, a finding of utmost epidemiological importance given its implication with congenital CMV infections.

Diagnostic and Biological Significance of KIR Expression Profile Determined by RNA-Seq in Natural Killer/T-Cell Lymphoma

Natural killer/T-cell lymphoma (NKTCL) is a rare, aggressive form of non-Hodgkin lymphoma that is generally incurable at more advanced stages with systemic involvement. Clonal diagnostic markers (eg, unique T- or B-cell receptor rearrangements) are not available for NKTCLs. Killer cell immunoglobulin like receptors (KIRs) are a family of type I transmembrane glycoproteins involved in the inhibition or activation of NK cells. A restricted expression profile of KIRs has been proposed as clonal markers of NK-cell proliferations. Here we evaluated the transcription profile of all KIR family genes and C-type lectin receptor genes using RNA sequencing on NKTCL cases (n = 17) and NK-cell lines (n = 3). The expression of all KIRs tended to be markedly reduced or absent in NKTCL, except for the KIR family member killer Ig-like receptor 2DL4 (KIR2DL4; alias CD158D), which was selectively overexpressed in the majority (59%) of cases. No specific expression pattern was observed for C-type lectin receptors. KIR2DL4 is an unusual member of the KIR family that recognizes human leukocyte antigen G and mediates NK-cell activation through inducing proliferation and survival pathways such as AKT and NF-κB. Stable knockdown of KIR2DL4 in two malignant NK-cell lines with high KIR2DL4 expression significantly reduced cell growth. Selective overexpression of KIR2DL4 and down-regulation of inhibitory KIRs may contribute to NKTCL pathogenesis.

Natural Killer Cell Diversity in Viral Infection: Why and How Much?

Natural killer cells are a diverse group of innate lymphocytes that are specialized to rapidly respond to cancerous or virus-infected cells. NK cell function is controlled by the integration of signals from activating and inhibitory receptors expressed at the cell surface. Variegated expression patterns of these activating and inhibitory receptors at the single cell level leads to a highly diverse NK cell repertoire. Here I review the factors that influence NK cell repertoire diversity and its functional consequences for our ability to fight viruses.

Donor Killer Immunoglobulin-Like Receptor Profile Bx1 Imparts a Negative Effect and Centromeric B-Specific Gene Motifs Render a Positive Effect on Standard-Risk Acute Myeloid Leukemia/Myelodysplastic Syndrome Patient Survival after Unrelated Donor Hematopoietic Stem Cell Transplantation

Donor killer immunoglobulin-like receptor (KIR) group B profiles (Bx) and homozygous of centromeric motif B (Cen-B/B) are the most preferable KIR gene content motifs for hematopoietic stem cell transplantation (HSCT). The risk of transplant from Bx1 donors and the benefit of the presence of Cen-B (regardless of number) were observed for standard-risk acute myeloid leukemia/myelodysplastic syndrome (AML/MDS) patients in this 4-year retrospective study. A total of 210 Chinese patients who underwent unrelated donor HSCT were investigated. Donor KIR profile Bx was associated with significantly improved overall survival (OS; P = .026) and relapse-free survival (RFS; P = .021) and reduced nonrelapse mortality (NRM; P = .017) in AML/MDS patients. A significantly lower survival rate was observed for transplants from Bx1 donors compared with Bx2, Bx3, and Bx4 donors for patients in first complete remission (n = 82; OS: P = .024; RFS: P = .021). Transplant from donors with Cen-B resulted in improved OS (HR = .256; 95% CI, .084 to .774; P = .016) and RFS (HR = .252; 95% CI, .084 to .758; P = .014) in AML/MDS patients at standard risk. However, this particular effect did not increase with a higher number of Cen-B motifs (cB/B versus cA/B; OS: P = .755; RFS: P = .768). No effect was observed on high-risk AML/MDS, acute lymphoblastic leukemia/non-Hodgkin lymphoma, and chronic myelogenous leukemia patients. Avoiding the selection of HSCT donors of KIR profile Bx1 is strongly advisable for standard-risk AML/MDS patients. The presence of the Cen-B motif rather than its number was more important in donor selection for the Chinese population.

Up-regulation of activating and inhibitory NKG2 receptors in allogeneic and autologous hematopoietic stem cell grafts

Background

Hematopoietic Stem Cell Transplantation (HSCT) is known to induce the inhibitory immune receptor NKG2A on NK cells of donor origin. This occurs in allogeneic recipients, in both the haploidentical and HLA-matched settings.

Methods

To gain further insight, not only NKG2A, but also the activating receptors NKG2C and NKG2D were assessed by flow cytometry. Immunophenotyping was carried out not only on CD56⁺ but also on CD8⁺ lymphocytes from leukemia and lymphoma patients, receiving both HLA-matched (n = 7) and autologous (n = 5) HSCT grafts. Moreover, cognate NKG2 ligands (HLA-E, MICA, ULBP-1, ULBP-2 and ULBP-3) were assessed by immunohistochemistry in diagnostic biopsies from three autotransplanted patients, and at relapse in one case.

Results

All the NKG2 receptors were simultaneously up-regulated in all the allotransplanted patients on CD8⁺ and/or CD56⁺ cells between 30 and 90 days post-transplant, coinciding with, or following, allogeneic engraftment. Up-regulation was of lesser entity and restricted to CD8⁺ cells in the autotransplantation setting. The phenotypic expression ratio between activating and inhibitory NKG2 receptors was remarkably similar in all the patients, except two outliers (a long survivor and a short survivor) who surprisingly displayed a similar NKG2 activation immunophenotype. Tumor expression of 2 to 3 out of the 5 tested NKG2 ligands was observed in 3/3 diagnostic biopsies, and 3 ligands were up-regulated post-transplant in a patient.

Conclusions

Altogether, these results are consistent with a dual (activation-inhibition) NK cell re-education mode, an innate-like T cell re-tuning, and a ligand:receptor interplay between the tumor and the immune system following HSCT including, most interestingly, the up-regulation of several activating NKG2 ligands. Turning the immune receptor balance toward activation on both T and NK cells of donor origin may complement ex vivo NK cell expansion/activation strategies in unmanipulated patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0213-y) contains supplementary material, which is available to authorized users.

Present and Future of Allogeneic Natural Killer Cell Therapy

Natural killer (NK) cells are innate lymphocytes that are capable of eliminating tumor cells and are therefore used for cancer therapy. Although many early investigators used autologous NK cells, including lymphokine-activated killer cells, the clinical efficacies were not satisfactory. Meanwhile, human leukocyte antigen (HLA)-haploidentical hematopoietic stem cell transplantation revealed the antitumor effect of allogeneic NK cells, and HLA-haploidentical, killer cell immunoglobulin-like receptor ligand-mismatched allogeneic NK cells are currently used for many protocols requiring NK cells. Moreover, allogeneic NK cells from non-HLA-related healthy donors have been recently used in cancer therapy. The use of allogeneic NK cells from non-HLA-related healthy donors allows the selection of donor NK cells with higher flexibility and to prepare expanded, cryopreserved NK cells for instant administration without delay for ex vivo expansion. In cancer therapy with allogeneic NK cells, optimal matching of donors and recipients is important to maximize the efficacy of the therapy. In this review, we summarize the present state of allogeneic NK cell therapy and its future directions.

Infusions of allogeneic natural killer cells as cancer therapy

Natural killer (NK) cells are normal white blood cells capable of killing malignant cells without prior sensitization. Allogeneic NK cell infusions are attractive for cancer therapy because of non-cross-resistant mechanisms of action and minimal overlapping toxicities with standard cancer treatments. Although NK therapy is promising, many obstacles will need to be overcome, including insufficient cell numbers, failure of homing to tumor sites, effector dysfunction, exhaustion, and tumor cell evasion. Capitalizing on the wealth of knowledge generated by recent NK cell biology studies and the advancements in biotechnology, substantial progress has been made recently in improving therapeutic efficiency and reducing side effects. A multipronged strategy is essential, including immunogenetic-based donor selection, refined NK cell bioprocessing, and novel augmentation techniques, to improve NK function and to reduce tumor resistance. Although data from clinical trials are currently limited primarily to hematologic malignancies, broader applications to a wide spectrum of adult and pediatric cancers are under way. The unique properties of human NK cells open up a new arena of novel cell-based immunotherapy against cancers that are resistant to contemporary therapies.

Novel insights in the genomic organization and hotspots of recombination in the human KIR locus through analysis of intergenic regions

The Killer Immunoglobulin-like Receptor (KIR) proteins constitute a family of highly homologous surface receptors involved in the regulation of the innate cytotoxicity of natural killer (NK) cells. Within the human genome, 17 KIR genes are present, many of which show large variation across the population owing to the high number of allelic variants and copy number variation (CNV). KIR genotyping and CNV determination were used to map the KIR locus in a large cohort of >400 Caucasian individuals. Gene order and structure was determined by sequence-specific polymerase chain reaction of the intergenic regions. In this way, we could show that KIR3DL1 and KIR2DS4 gene variants are linked and that--contrary to current views--the gene KIR2DS5 is only present in the telomeric half of the KIR locus. Our study revealed novel insights in the highly organized distribution of KIR genes. Novel recombination hotspots were identified that contribute to the diversity of KIR gene distribution in the Caucasian population. Next-generation sequencing of the KIR intergenic regions allowed for a detailed single-nucleotide polymorphism analysis, which demonstrated several gene-specific as well as haplotype-specific nucleotides for a more accurate genotyping of this notoriously complex gene cluster.

The impact of HLA and KIR ligand mismatching on unrelated allogeneic hematopoietic stem cell transplantation in Korean adult patients

Background

The impact of HLA and KIR ligand mismatching on the outcome of hematopoietic stem cell transplantation (HSCT) remains unclear. Previous reports have identified considerable ethnic differences in the impact of HLA and KIR ligand mismatches, as well as KIR ligand status, on HSCT; however, to date, no data has been acquired in Korean adult patients.

Methods

We investigated the association of high-resolution HLA matching on five loci (HLA-A, -B, -C, -DRB1, and -DQB1), KIR ligand mismatching, and KIR ligand status on the outcome of allogeneic HSCT from unrelated donors in 154 Korean adult patients treated at Seoul National University Hospital.

Results

In a multivariate analysis, less than 9/10 allelic matches in five HLA loci was an independent risk factor for acute graft-versus-host disease (GVHD) (grade II to IV) (P=0.019, odds ratio [OR]=2.7). In addition, HLA-A allele mismatching was increasingly prevalent in patients with acute GVHD compared to patients without (61.9% vs. 34.5%, P=0.06). For KIR ligand status, the patient and donor combination of both C1/C1 ligands showed better event-free and overall survival than combinations with C2 ligand patients or donors (P=0.048, P=0.034, respectively) by log-rank test.

Conclusions

Korean adult transplant patients with less than 9 of 10 HLA allele matches in the HLA-A, -B, -C, -DRB1, and DQB1 loci have a higher likelihood of developing acute GVHD (grade II to IV). Impact of KIR ligand status on clinical outcome should be further studied in a larger patient population.

Donor Haplotype B of NK KIR Receptor Reduces the Relapse Risk in HLA-Identical Sibling Hematopoietic Stem Cell Transplantation of AML Patients

Successful allogeneic hematopoietic stem cell transplantation (HSCT) depends not only on good HLA match but also on T-cell mediated graft-versus-leukemia (GvL) effect. Natural killer (NK) cells are able to kill malignant cells by receiving activation signal from the killer-cell immunoglobulin-like receptors (KIR) recognizing HLA molecules on a cancer cell. It has been recently reported that the risk of relapse in allogeneic hematopoietic stem cell transplantation (HSCT) is reduced in acute myeloid leukemia (AML) patients whose donors have several activating KIR genes or KIR B-motifs in unrelated donor setting, obviously due to enhanced GvL effect by NK cells. We studied the effect on relapse rate of donor KIR haplotypes in the HLA-identical adult sibling HSCT, done in a single center, in Helsinki University Central Hospital, Helsinki, Finland. Altogether, 134 patients with 6 different diagnoses were identified. Their donors were KIR genotyped using the Luminex and the SSP techniques. The clinical endpoint, that is, occurrence of relapse, was compared with the presence or absence of single KIR genes. Also, time from transplantation to relapse was analyzed. The patients with AML whose donors have KIR2DL2 or KIR2DS2 had statistically significantly longer relapse-free survival (P = 0.015). Our data support previous reports that donors with KIR B-haplotype defining genes have a lower occurrence of relapse in HSCT of AML patients. Determination of donor KIR haplotypes could be a useful addition for a risk assessment of HSCT especially in AML patients.

Presence of more activating KIR genes is associated with Hashimoto's thyroiditis

Killer cell immunoglobulin-like receptors (KIR) regulate the effector function of natural killer (NK) cells and the subset of T cells with memory phenotype. The number and type of genes that encode KIR receptors substantially varied between individuals and between populations. Specific KIR receptors are known to be associated with certain diseases. The present study was undertaken to investigate if any specific KIR gene(s) is associated with the susceptibility to Hashimoto's thyroiditis (HT), an inflammatory disease characterized by lymphocytic infiltration of the thyroid gland and the presence of autoantibodies directed against thyroglobulin and/or thyroid peroxidase. DNA from 118 patients with HT and 120 healthy controls was characterized for the presence and absence of 11 variable KIR genes using a gene-specific PCR typing system. Although no significant difference in the frequency of individual KIR genes between patients and controls was detected, more patients carry the six activating KIR genes compared with the control group (11.8 vs. 4.1 %, p = 0.032, OR = 3.09, 95 % CI 1.07-8.89). The data suggest that augmented signals from multiple activating KIR receptors might exacerbate the activation of NK cells and T cell subsets against self-antigens, thus contributing to the pathogenesis of HT.

Extracellular HCV-core protein induces an immature regulatory phenotype in NK cells: implications for outcome of acute infection

Background

Hepatitis C viral (HCV) proteins, including core, demonstrate immuno-modulatory properties; however, the effect of extracellular core on natural killer (NK) cells has not previously been investigated.

Aims

To characterise NKs in acute HCV infection over time, and, to examine the effect of exogenous HCV-core protein on NK cell phenotype and function.

Methods

Acute HCV patients (n = 22), including 10 subjects who spontaneously recovered, were prospectively studied. Flow-cytometry was used to measure natural cytotoxicity and to phenotype NKs directly ex vivo and after culture with HCV-core protein. Microarray analysis was used to identify pathways involved in the NK cell response to exogenous HCV-core.

Results

Direct ex vivo analysis demonstrated an increased frequency of immature/regulatory CD56^bright NKs early in acute HCV infection per se which normalized with viral clearance. Natural cytotoxicity was reduced and did not recover after viral clearance. There was a statistically significant correlation between the frequency of CD56^bright NKs and circulating serum levels of HCV core protein. In vitro culture of purified CD56^bright NK cells with HCV-core protein in the presence of IL-15 maintained a significant proportion of NKs in the CD56^bright state. The in vitro effect of core closely correlates with NK characteristics measured directly ex vivo in acute HCV infection. Pathway analysis suggests that HCV-core protein attenuates NK interferon type I responses.

Conclusions

Our data suggest that HCV-core protein alters NK cell maturation and may influence the outcome of acute infection.

Donor killer cell Ig-like receptor B haplotypes, recipient HLA-C1, and HLA-C mismatch enhance the clinical benefit of unrelated transplantation for acute myelogenous leukemia

Killer cell Ig-like receptors (KIRs) interact with HLA class I ligands to regulate NK cell development and function. These interactions affect the outcome of unrelated donor hematopoietic cell transplantation (HCT). We have shown previously that donors with KIR B versus KIR A haplotypes improve the clinical outcome for patients with acute myelogenous leukemia by reducing the incidence of leukemic relapse and improving leukemia-free survival (LFS). Both centromeric and telomeric KIR B genes contribute to the effect, but the centromeric genes are dominant. They include the genes encoding inhibitory KIRs that are specific for the C1 and C2 epitopes of HLA-C. We used an expanded cohort of 1532 T cell-replete transplants to examine the interaction between donor KIR B genes and recipient class I HLA KIR ligands. The relapse protection associated with donor KIR B is enhanced in recipients who have one or two C1-bearing HLA-C allotypes, compared with C2 homozygous recipients, with no effect due to donor HLA. The protective interaction between donors with two or more, versus none or one, KIR B motifs and recipient C1 was specific to transplants with class I mismatch at HLA-C (RR of leukemia-free survival, 0.57 [0.40-0.79]; p = 0.001) irrespective of the KIR ligand mismatch status of the transplant. The survival advantage and relapse protection in C1/x recipients compared with C2/C2 recipients was similar irrespective of the particular donor KIR B genes. Understanding the interactions between donor KIR and recipient HLA class I can be used to inform donor selection to improve outcome of unrelated donor hematopoietic cell transplantation for acute myelogenous leukemia.

Recognition of tumors by the innate immune system and natural killer cells

In recent years, roles of the immune system in immune surveillance of cancer have been explored using a variety of approaches. The roles of the adaptive immune system have been a major emphasis, but increasing evidence supports a role for innate immune effector cells such as natural killer (NK) cells in tumor surveillance. Here, we discuss some of the evidence for roles in tumor surveillance of innate immune cells. In particular, we focus on NK cells and other immune cells that express germline-encoded receptors, often labeled NK receptors. The impact of these receptors and the cells that express them on tumor suppression is summarized. We discuss in detail some of the pathways and events in tumor cells that induce or upregulate cell-surface expression of the ligands for these receptors, and the logic of how those pathways serve to identify malignant, or potentially malignant cells. How tumors often evade tumor suppression mediated by innate killer cells is another major subject of the review. We end with a discussion on some of the implications of the various findings with respect to possible therapeutic approaches.

Natural killer cells and killer-cell immunoglobulin-like receptor polymorphisms: their role in hematopoietic stem cell transplantation

Natural killer (NK) cells are important effector cells in the early control of infected, malignant, and "nonself" cells. Various receptor families are involved in enabling NK cells to detect and efficiently eliminate these target cells. The killer-cell immunoglobulin-like receptor (KIR) family is a set of receptors that are very polymorphic with regard to gene content, expression level, and expression pattern. KIRs are responsible for the induction of a NK cell alloreactive response through their interaction with HLA class I molecules. The role of NK cells in hematopoietic stem cell transplantation (HSCT) has been studied for many years, and induction of antileukemic responses by donor NK cells has been reported. Conflicting data still exist on the exact circumstances in which the KIR repertoire affects and influences clinical outcome after HSCT. More large-scale studies are needed on well-defined cohorts to unravel the mechanism of action of the NK cell-mediated alloresponse in an HSCT setting.

Selective expansion of human natural killer cells leads to enhanced alloreactivity

In allogeneic stem cell transplantation (SCT), natural killer (NK) cells lacking their cognate inhibitory ligand can induce graft-versus-leukemia responses, without the induction of severe graft-versus-host disease (GVHD). This feature can be exploited for cellular immunotherapy. In this study, we examined selective expansion of NK cell subsets expressing distinct killer immunoglobulin-like receptors (KIRs) within the whole human peripheral blood NK cell population, in the presence of HLA-Cw3 (C1) or Cw4 (C2) transfected K562 stimulator cells. Coculture of KIR(+) NK cells with C1 or C2 positive K562 cells, in the presence of IL-2+IL-15, triggered the outgrowth of NK cells that missed their cognate ligand. This resulted in an increased frequency of alloreactive KIR(+) NK cells within the whole NK cell population. Also, after preculture with K562 cells lacking their cognate ligand, we observed that this alloreactive NK population revealed higher numbers of CD107(+) cells when cocultured with the relevant K562 HLA-C transfected target cells, as compared to coculture with untransfected K562 cells. This enhanced reactivity was confirmed using primary leukemic cells as target. This study demonstrates that HLA class I expression can mediate the skewing of the NK cell repertoire and enrich the population for cells with enhanced alloreactivity towards leukemic target cells. This feature may support future clinical applications of NK cell-based immunotherapy.

Genetic and environmental determinants of human NK cell diversity revealed by mass cytometry

Natural killer (NK) cells play critical roles in immune defense and reproduction, yet remain the most poorly understood major lymphocyte population. Because their activation is controlled by a variety of combinatorially expressed activating and inhibitory receptors, NK cell diversity and function are closely linked. To provide an unprecedented understanding of NK cell repertoire diversity, we used mass cytometry to simultaneously analyze 37 parameters, including 28 NK cell receptors, on peripheral blood NK cells from 5 sets of monozygotic twins and 12 unrelated donors of defined human leukocyte antigen (HLA) and killer cell immunoglobulin-like receptor (KIR) genotype. This analysis revealed a remarkable degree of NK cell diversity, with an estimated 6000 to 30,000 phenotypic populations within an individual and >100,000 phenotypes in the donor panel. Genetics largely determined inhibitory receptor expression, whereas activation receptor expression was heavily environmentally influenced. Therefore, NK cells may maintain self-tolerance through strictly regulated expression of inhibitory receptors while using adaptable expression patterns of activating and costimulatory receptors to respond to pathogens and tumors. These findings further suggest the possibility that discrete NK cell subpopulations could be harnessed for immunotherapeutic strategies in the settings of infection, reproduction, and transplantation.

Emerging role for the killer-cell immunoglobulin-like receptors genotype, in the susceptibility of skin diseases

NK cells are a major group of immune cells responsible for the phenomenon of natural, innate cytotoxicity. One of the better studied receptors of human NK cells are killer cell immunoglobulin-like receptors (KIR) responsible for checking the presence of MHC class I molecules, which serve as their ligands. Although previously treated as specific for NK cells, nowadays these receptors are known to also occur on T cells. Genetics of KIR molecules is very complicated, what create a great variability of haplotypes in various populations world-wide. In addition, some KIR are known to recognize HLA-C (epitopes C1 or C2), HLA-B (Bw4) or HLA-A (A3 and/or A11) molecules. Therefore, this makes a huge diversity of reactions among individuals, depending on the presence or absence of given KIR and their ligands, hence differential susceptibility to several diseases, including various dermatoses. This paper underlines the important role of both KIR genotypes and HLA class I genes with reference to the various skin diseases.

Natural killer cell inhibitory receptor expression in humans and mice: a closer look

The Natural Killer (NK) cell population is composed of subsets of varying sizes expressing different combinations of inhibitory receptors for MHC class I molecules. Genes within the NK gene complex, including the inhibitory receptors themselves, seem to be the primary intrinsic regulators of inhibitory receptor expression, but the MHC class I background is an additional Modulating factor. In this paper, we have performed a parallel study of the inhibitory receptor repertoire in inbred mice of the C57Bl/6 background and in a cohort of 44 humans. Deviations of subset frequencies from the “product rule (PR),” i.e., differences between observed and expected frequencies of NK cells, were used to identify MHC-independent and MHC-dependent control of receptor expression frequencies. Some deviations from the PR were similar in mice and humans, such as the decreased presence of NK cell subset lacking inhibitory receptors. Others were different, including a role for NKG2A in determining over- or under-representation of specific subsets in humans but not in mice. Thus, while human and murine inhibitory receptor repertoires differed in details, there may also be shared principles governing NK cell repertoire formation in these two species.

HLA reduces killer cell Ig-like receptor expression level and frequency in a humanized mouse model

NK cells use NK cell receptors to be able to recognize and eliminate infected, transformed, and allogeneic cells. Human NK cells are prevented from killing autologous healthy cells by virtue of inhibitory NKRs, primarily killer cell Ig-like receptors (KIR) that bind "self" HLA class I molecules. Individual NK cells stably express a selected set of KIR, but it is currently disputed whether the fraction of NK cells expressing a particular inhibitory KIR is influenced by the presence of the corresponding HLA ligand. The extreme polymorphism of the KIR and HLA loci, with wide-ranging affinities for individual KIR and HLA allele combinations, has made this issue particularly hard to tackle. In this study, we used a transgenic mouse model to investigate the effect of HLA on KIR repertoire and function in the absence of genetic variation inside and outside the KIR locus. These H-2K(b-/-) and H-2D(b-/-) mice lacked ligands for inhibitory Ly49 receptors and were transgenic for HLA-Cw3 and a KIR B haplotype. In this reductionist system, the presence of HLA-Cw3 reduced the frequency of KIR2DL2(+) cells, as well as the surface expression levels of KIR2DL2. In addition, in the presence of HLA-Cw3, the frequency of NKG2A(+) cells and the surface expression levels of NKG2A were reduced. In line with these findings, both transgene-encoded KIR and endogenous NKG2A contributed to the rejection of cells lacking HLA-Cw3. These findings support the idea that HLA influences the human KIR repertoire.