Natural Killer Cell Alloreactivity in Haploidentical Hematopoietic Stem Cell Transplantation

Natural killer (NK) cells are primed to kill by several activating receptors. NK cell killing of autologous cells is prevented because NK cells coexpress inhibitory receptors (killer cell immunoglobulin-like receptors [KIR]) that recognize groups of (self) major histocompatibility complex class I alleles. Because KIRs are clonally distributed, the NK cell population in any individual are constituted of a repertoire with a variety of class I specificities. NK cells in the repertoire mediate alloreactions when the allogeneic targets do not express the class I alleles that block them. After haploidentical hematopoietic transplantation, NK cell-mediated donor-versus-recipient alloresponses reduce the risk of relapse in acute myeloid leukemia patients while improving engraftment and protecting against graft-versus-host disease. High-resolution molecular HLA typing of recipient and donor, positive identification of donor KIR genes, and, in some cases, functional assessment of donor NK clones identify haploidentical donors who are able to mount donor-versus-recipient NK alloreactions.     

Genotypic inhibitory killer immunoglobulin-like receptor ligand incompatibility enhances the long-term antileukemic effect of unmodified allogeneic hematopoietic stem cell transplantation in patients with myeloid leukemias

It remains controversial whether alloreactive donor-derived natural killer (NK) cells display graft-versus-leukemia reactions after unmodified allogeneic hematopoietic stem cell transplantation (HSCT). The present study evaluated the role of inhibitory killer immunoglobulin-like receptor (KIR) ligand incompatibility using a well-defined and uniform setting of unmodified allogeneic HSCT in 374 patients with myeloid leukemias. The most striking finding was a significant heterogeneity in the 5-year estimates of hematologic leukemic relapse after human leukocyte antigen (HLA)-identical (n = 237; 22%), HLA class I-disparate (n = 89; 18%), and KIR ligand-incompatible transplantations (n = 48; 5%) (P < .04). Multivariate analysis confirmed that the relative relapse risk (RR) was influenced by HLA class I disparity alone (RR 0.49), but was lowest after HLA class I-disparate, KIR ligand-incompatible transplantations (RR 0.24) (P < .008). The primary graft failure rates, however, increased from 0.4% after HLA class I-identical to 2.3% after HLA class I-disparate, and to 6.3% after KIR ligand-incompatible transplantations, respectively (P < .02). Unlike some other reports, no beneficial effect of KIR ligand incompatibility on other major endpoints of allogeneic HSCT (transplantation-related mortality, and overall and event-free survival) was detectable in the present study. In conclusion, unmodified allogeneic HSCT from KIR ligand-incompatible donors provides a superior long-term antileukemic efficacy in patients with myeloid malignancies.     

Alloreactive natural killer cells in mismatched hematopoietic stem cell transplantation

Natural killer (NK) cell-mediated, donor-vs.-recipient alloresponses occur following transplantation of human leukocyte antigen (HLA) haplotype-mismatched hematopoietic stem cells (HSCs). NK cell alloreactivity reduced the risk of relapse in acute myeloid leukemia patients while improving engraftment and protecting against graft-vs.-host disease (GvHD). NK cells are primed to kill by several activating receptors. NK killing of autologous cells is prevented because NK cells co-express inhibitory receptors (killer cell Ig-like receptors, KIR) that recognize groups of (self) MHC class I alleles. As KIRs are clonally distributed, the NK population in any individual is constituted of a repertoire with different allospecificities. NK cells in the repertoire mediate alloreactions when the allogeneic targets do not express class I alleles that block them. High resolution molecular HLA typing of recipient and donor, positive identification of donor KIR genes, and in some cases, functional assessment of donor NK clones will identify haploidentical donors who are able to mount donor-vs.-recipient NK alloreactions.     

Role of natural killer cell alloreactivity in HLA-mismatched hematopoietic stem cell transplantation.

Because of the expression of inhibitory receptors (KIR) for major histocompatibility complex (MHC) class I allotypes, a person's natural killer (NK) cells will not recognize and will, therefore, kill cells from individuals lacking his/her KIR epitopes. This study investigated the role of NK cell alloreactivity in human HLA haplotype-mismatched hematopoietic stem cell transplantation and, specifically, the role of the three major NK specificities, ie, those for HLA-C group 1, HLA-C group 2, and HLA-Bw4 alleles. In 20 of 60 donor-recipient pairs, KIR epitope incompatibility and functional analyses of donor NK cell clones predicted donor NK cells could cause graft-versus-host (GVH)/graft-versus-leukemia (GVL) reactions. NK cell clones of donor origin were obtained from transplanted recipients and tested for lysis of recipient's cryopreserved pretransplant lymphocytes. Despite the absence of GVH disease, we detected high frequencies of NK clones which killed recipient's target cells. Lysis followed the rules of NK cell alloreactivity, being blocked only by the MHC class I KIR epitope which was missing in the recipient. The alloreactive NK clones also killed the allogeneic leukemia. Transplants from these KIR epitope incompatible donors had higher engraftment rates. Therefore, a GVL effector and engraftment facilitating mechanism, which is independent of T-cell-mediated GVH reactions, may be operational in HLA mismatched hematopoietic cell transplants.     

Single-cell analysis of the human NK cell response to missing self and its inhibition by HLA class I

Natural killer (NK) cells activate quickly in response to pathogens, tumors, and allogeneic hematopoietic cell transplants. Modulating the NK cell response are clonally distributed NK cell receptors that survey cells for change in the expression of major histocompatibility complex (MHC) class I and structurally related ligands. Here the enzyme-linked immunospot (ELISPOT) assay, intracellular cytokine staining (ICS), and short-term culture were used to quantify the response of bulk NK cell populations from human donors to HLA class I-deficient 221 cells and to 221 cells transfected with single HLA class I allotypes. NK cells in cultures containing interleukin-2 (IL-2) or IL-12 exhibited specificities of HLA class I-mediated inhibition that correlated well with those previously defined using NK cell clones in long-term culture and with the frequencies of cells expressing particular inhibitory HLA class I receptors. Culture with IL-12, but not IL-2, gave an increased frequency of cells expressing CD94: NKG2A but no change in killer immunoglobulin-like receptor (KIR) expression. For some heterozygote combinations of KIR3DL1 alleles, ICS can be used to compare the functional properties of the 2 allotypes. Thus, both the low-expressing KIR3DL1*005 and the high-expressing KIR3DL1*002 gave similar inhibitory response on challenge with an HLA-B*5801 ligand. The single-cell assays developed here should facilitate future population study and clinical analysis of human NK cell regulation by MHC class I.     

Functional inhibitory human leucocyte antigen class I receptors on natural killer (NK) cells in patients with chronic NK lymphocytosis

Chronic natural killer (NK) lymphocytosis is a rare disorder characterized by an indolent clinical course. Despite high NK cell numbers, many patients present with only mild clinical symptoms, and are often asymptomatic. NK cells are equipped with a range of receptors that bind human leucocyte antigen (HLA)-class I molecules. The killer immunoglobulin-like receptors (KIR, CD158) bind groups of HLA alleles, the CD94/NKG2 receptors bind HLA-E, and the CD85j (ILT2, LIR-1) receptor binds to the relatively non-polymorphic alpha3 domain of HLA molecules. Inhibitory HLA class I receptors silence NK cells against cells expressing normal levels of HLA class I. Analysis of NK cells in six patients with chronic NK lymphocytosis revealed a high level of the inhibitory CD94/NKG2A receptor on all NK cells. In four patients, KIR were absent, in one patient a single KIR was expressed in the absence of self-ligand, and in one patient CD85j and multiple KIR were expressed. Cytotoxicity assays demonstrated that all HLA class I receptors were functional. The ability of monoclonal antibodies to block the receptors and allow killing of autologous target cells established that both receptor and ligand expression were adequate for inhibitory function. We propose that the silent behaviour of NK cells in patients with chronic NK lymphocytosis is due to effective inhibitory HLA class I receptors.     

Natural killer cells as a therapeutic tool in mismatched transplantation

Natural-killer-cell-mediated, donor-vs-recipient alloresponses occur following transplantation of human-leukocyte-antigen (HLA)-haplotype-mismatched haematopoietic stem cells. Natural killer (NK) cell alloreactivity reduces the risk of relapse in acute myeloid leukaemia patients, while improving engraftment and protecting against graft-vs-host disease. NK cells are primed to kill by several activating receptors. NK cell killing of autologous cells is prevented as NK cells co-express inhibitory receptors (killer cell Ig-like receptors, KIR) that recognize groups of (self) major histocompatibility complex class I alleles. As KIRs are distributed clonally, the NK cell population in any individual constitutes a repertoire with different allospecificities. NK cells in the repertoire mediate alloreactions when the allogeneic targets do not express class I alleles that block them. High-resolution molecular HLA typing of recipient and donor, positive identification of donor KIR genes and, in some cases, functional assessment of donor NK clones will identify haplo-identical donors who are able to mount donor-vs-recipient NK alloreactions.     

Killer Ig-like receptor-mediated control of natural killer cell alloreactivity in haploidentical hematopoietic stem cell transplantation

Natural killer (NK) cells are key members of the innate immune system. In a self-environment, they sense and kill target cells lacking major histocompatibility complex class I molecules and release various cytokines on activation. The discovery of human leukocyte antigen (HLA) class I specific inhibitory receptors (including the allotype-specific killer immunoglobulin-like receptors), and of various activating receptors and their ligands, provided the basis for understanding the molecular mechanism of NK-cell activation and function, mainly resulting from the balance between activating and inhibitory signals. In an allogeneic setting, such as T cell-depleted haploidentical hematopoietic stem cell transplantation, NK cells may express inhibitory killer immunoglobulin-like receptors that are not engaged by any of the HLA class I alleles present on allogeneic cells. Such "alloreactive" NK cells greatly contribute both to eradication of leukemia blasts escaping the preparative regimen and to clearance of residual host dendritic cells and T lymphocytes (thus preventing graft-versus-host disease and graft rejection, respectively). Improved prevention of graft-versus-host disease might be achieved by redirecting to lymph nodes adoptively transferred, alloreactive NK cells by inducing CCR7-uptake in vitro. Recent studies suggested that, after immune-suppressive therapy, alloreactive NK cells from an HLA-haploidentical donor may prevent leukemia recurrence also in patients who have not received allogeneic hematopoietic stem cell transplantation.     

The reactivity of Bw4+ HLA-B and HLA-A alleles with KIR3DL1: implications for patient and donor suitability for haploidentical stem cell transplantations

Natural killer (NK)–cell alloreactivity can be exploited in haploidentical hematopoietic stem cell transplantation (HSCT). NK cells from donors whose HLA type includes Bw4, a public epitope present on a subset of HLA-B alleles, can be alloreactive toward recipients whose cells lack Bw4. Serologically detectable epitopes related to Bw4 also exist on a subset of HLA-A alleles, but the interaction of these alleles with KIR3DL1 is controversial. We therefore undertook a systematic analysis of the ability of most common HLA-B alleles and HLA-A alleles with Bw4 serologic reactivity to protect target cells from lysis by KIR3DL1-dependent NK cells. All Bw4^– HLA-B alleles failed to protect target cells from lysis. All Bw4⁺ HLA-B alleles with the exception of HLA-B*1301 and -B*1302 protected targets from lysis. HLA-A*2402 and HLA-A*3201 unequivocally protected target cells from lysis, whereas HLA-A*2501 and HLA-A*2301 provided only weak protection from lysis. KIR3DL1-dependent alloreactive NK clones were identified in donors with HLA-A*2402 but not in donors with HLA-B*1301 or -B*1302. These findings clarify the HLA types that donors and recipients need in haploidentical HSCT and other NK allotherapies in order to benefit from NK alloreactivity.     

T-cell alloreactivity dominates natural killer cell alloreactivity in minimally T-cell-depleted HLA-non-identical paediatric bone marrow transplantation

Natural killer (NK) cell alloreactivity resulting from killer immunoglobulin-like receptor (KIR) ligand incompatibility improves outcomes in patients receiving extensively T-cell-depleted bone marrow (BM) grafts. Patients with KIR ligand incompatibility are at risk for donor T-cell alloreactivity. We investigated the relative significance of NK-cell and T-cell alloreactivity in 105 paediatric patients who received a minimally T-cell-depleted human leucocyte antigen-non-identical BM transplantation. Donor NK-cell incompatibility did not improve patient outcome [engraftment, graft-versus-host disease (GVHD), relapse or overall survival]. In contrast, donor T-cell incompatibility was a risk factor for acute GVHD, chronic GVHD and death. Thus, T-cell alloreactivity dominated that of NK cells in minimally T-cell-depleted grafts.     

Co-evolution of KIR2DL3 with HLA-C in a human population retaining minimal essential diversity of KIR and HLA class I ligands

Natural killer (NK) cells contribute to immunity and reproduction. Guiding these functions, and NK cell education, are killer cell Ig-like receptors (KIR), NK cell receptors that recognize HLA class I. In most human populations, these highly polymorphic receptors and ligands combine with extraordinary diversity. To assess how much of this diversity is necessary, we studied KIR and HLA class I at high resolution in the Yucpa, a small South Amerindian population that survived an approximate 15,000-year history of population bottleneck and epidemic infection, including recent viral hepatitis. The Yucpa retain the three major HLA epitopes recognized by KIR. Through balancing selection on a few divergent haplotypes the Yucpa maintain much of the KIR variation found worldwide. HLA-C*07, the strongest educator of C1-specific NK cells, has reached unusually high frequency in the Yucpa. Concomitantly, weaker variants of the C1 receptor, KIR2DL3, were selected and have largely replaced the form of KIR2DL3 brought by the original migrants from Asia. HLA-C1 and KIR2DL3 homozygosity has previously been correlated with resistance to viral hepatitis. Selection of weaker forms of KIR2DL3 in the Yucpa can be seen as compensation for the high frequency of the potent HLA-C*07 ligand. This study provides an estimate of the minimal KIR-HLA system essential for long-term survival of a human population. That it contains all functional elements of KIR diversity worldwide, attests to the competitive advantage it provides, not only for surviving epidemic infections, but also for rebuilding populations once infection has passed.     

Killer cell immunoglobulin-like receptors influence the innate and adaptive immune responses

Natural killer (NK) cells are a subset of lymphocytes which play a crucial role in early innate immune response against infection and tumor transformation. Furthermore, they secrete interferon- (IFN-) and tumor necrosis factor (TNF) prompting adaptive immunity. NK cells distinguish the unhealthy cells from the healthy ones through an array of cell-surface receptors. Human NK cells use inhibitory and activating killer cell Ig-like receptors (KIR) as primary probe to discriminate between healthy and unhealthy cells. The inhibitory KIRs recognize HLA class I molecules and trigger signals that stop NK killing. The activating KIRs are believed to recognize the determinants associated with infections and tumors, and trigger signals that activate NK killing. Therefore, the effector function of a given NK cell depends upon the receptors that it expresses and ligands that it recognizes on the targets. Genes encoding KIRs and HLA ligands are located on different chromosomes, and vary in number and type. The independent segregation of KIR and HLA genes results in variable KIR-HLA combinations in individuals, which may determine the individual's immunity and susceptibility to disease.     

HLA alleles determine differences in human natural killer cell responsiveness and potency

Epidemiological studies have associated certain human disease outcomes with particular killer cell Ig-like receptor (KIR) and HLA genotypes. However, the functional explanation for these associations is poorly understood, because the KIRs were initially described as natural killer (NK) cell inhibitory receptors with specificity for HLA molecules on their cellular targets. Yet resolution of infections is often associated with genotypic pairing of inhibitory KIRs with their cognate HLA ligands. Recent studies in mice indicate a second role for MHC-specific inhibitory receptors, i.e., self-MHC recognition confers functional competence on the NK cell to be triggered through their activation receptors, a process termed licensing. As a result, licensed NK cells with self-MHC-specific receptors are more readily activated as compared with unlicensed NK cells without self-MHC-specific receptors. Such results predict that human NK cells may undergo a similar process. Here, we examined the human NK cell subset expressing KIR3DL1, the only known KIR specific for HLA-Bw4 alleles. The KIR3DL1(+) subset in normal donors with two HLA-B-Bw4 genes displayed increased responsiveness to tumor stimulation compared with the KIR3DL1(+) subset from individuals with only one or no Bw4 genes. By contrast, NK cells lacking KIR3DL1 showed no differences. Therefore, these data indicate that particular KIR and HLA alleles are associated with more responsive NK cells, strongly suggesting that human NK cells are also subjected to NK cell licensing, and providing a potential functional explanation for the influence of KIR and HLA genes in disease as well as interindividual differences in NK cell potency.     

Enhanced cytotoxicity of allogeneic NK cells with killer immunoglobulin-like receptor ligand incompatibility against melanoma and renal cell carcinoma cells

Cellular inactivation through killer immunoglobulin-like receptors (KIRs) may allow neoplastic cells to evade host natural killer (NK) cell-mediated immunity. Recently, alloreactive NK cells were shown to mediate antileukemic effects against acute myelogenous leukemia (AML) after mismatched transplantation, when KIR ligand incompatibility existed in the direction of graft-versus-host disease (GVHD). Therefore, we investigated whether solid tumor cells would have similar enhanced susceptibility to allogeneic KIR-incompatible NK cells compared with their KIR-matched autologous or allogeneic counterparts. NK populations enriched and cloned from the blood of cancer patients or healthy donors homozygous for HLA-C alleles in group 1 (C-G1) or group 2 (C-G2) were tested in vitro for cytotoxicity against Epstein-Barr virus-transformed lymphoblastic cell lines (EBV-LCLs), renal cell carcinoma (RCC), and melanoma (MEL) cells with or without a matching KIR-inhibitory HLA-C ligand. Allogeneic NK cells were more cytotoxic to tumor targets mismatched for KIR ligands than their KIR ligand-matched counterparts. Bulk NK populations (CD3(-)/CD2(+)/CD56(+)) expanded 10(4)-fold from patients homozygous for C-G1 or C-G2 had enhanced cytotoxicity against KIR ligand-mismatched tumor cells but only minimal cytotoxicity against KIR ligand-matched targets. Further, NK cell lines from C-G1 or C-G2 homozygous cancer patients or healthy donors expanded but failed to kill autologous or KIR-matched MEL and RCC cells yet had significant cytotoxicity (more than 50% lysis at 20:1 effector-target [E/T] ratio) against allogeneic KIR-mismatched tumor lines. These data suggest immunotherapeutic strategies that use KIR-incompatible allogeneic NK cells might have superior antineoplastic effects against solid tumors compared with approaches using autologous NK cells.     

Anti-leukemia activity of alloreactive NK cells in KIR ligand-mismatched haploidentical HSCT for pediatric patients: evaluation of the functional role of activating KIR and redefinition of inhibitory KIR specificity

We analyzed 21 children with leukemia receiving haploidentical hematopoietic stem cell transplantation (haplo-HSCT) from killer immunoglobulin (Ig)-like receptors (KIR) ligand-mismatched donors. We showed that, in most transplantation patients, variable proportions of donor-derived alloreactive natural killer (NK) cells displaying anti-leukemia activity were generated and maintained even late after transplantation. This was assessed through analysis of donor KIR genotype, as well as through phenotypic and functional analyses of NK cells, both at the polyclonal and clonal level. Donor-derived KIR2DL1(+) NK cells isolated from the recipient displayed the expected capability of selectively killing C1/C1 target cells, including patient leukemia blasts. Differently, KIR2DL2/3(+) NK cells displayed poor alloreactivity against leukemia cells carrying human leukocyte antigen (HLA) alleles belonging to C2 group. Unexpectedly, this was due to recognition of C2 by KIR2DL2/3, as revealed by receptor blocking experiments and by binding assays of soluble KIR to HLA-C transfectants. Remarkably, however, C2/C2 leukemia blasts were killed by KIR2DL2/3(+) (or by NKG2A(+)) NK cells that coexpressed KIR2DS1. This could be explained by the ability of KIR2DS1 to directly recognize C2 on leukemia cells. A role of the KIR2DS2 activating receptor in leukemia cell lysis could not be demonstrated. Altogether, these results may have important clinical implications for the selection of optimal donors for haplo-HSCT.     

Survival advantage with KIR ligand incompatibility in hematopoietic stem cell transplantation from unrelated donors

Killer immunoglobulin-like receptor (KIR) ligand incompatibility in the graft-versus-host direction was demonstrated to be associated with improved outcome in patients given haploidentical, T-cell-depleted hematopoietic stem cell transplants (HSCTs). The goal of this study was to evaluate whether that observation could be generalized for patients receiving unmanipulated HSCTs from unrelated donors (URD). One hundred thirty patients with hematologic malignancies entered the study. Graft-versus-host disease (GVHD) prophylaxis was uniform and consisted of cyclosporin, short-term methotrexate, and pretransplantation antithymocyte globulin (ATG). Patients were divided into those with (n = 20) and those without (n = 110) KIR ligand incompatibility with respect to their donors. At 4.5 years patients with KIR ligand incompatibility had higher probability of overall survival (87% versus 48%, P =.006) and disease-free survival (87% versus 39%, P =.0007) compared with those without KIR ligand incompatibility. Transplant-related mortality for the 2 groups equaled 6% and 40% (P =.01), respectively. Relapse rates for patients receiving transplants from a donor with or without KIR ligand incompatibility were 6% and 21%, respectively (P =.07). All patients with myeloid malignancies receiving transplants from KIR ligand-disparate donors (n = 13) are alive and disease free. These data indicate that natural killer (NK) cell alloreactivity is associated with better outcome after URD-HSC transplantation when ATG is used as part of GVHD prophylaxis.     

Improved outcome in HLA-identical sibling hematopoietic stem-cell transplantation for acute myelogenous leukemia predicted by KIR and HLA genotypes

Inhibitory killer immunoglobulin (Ig)-like receptors (KIRs) recognize HLA-C and -B epitopes on target cells, thereby regulating natural killer (NK) cell activity. In 178 patients receiving T-cell-depleted HLA-identical sibling transplants for acute myelogenous leukemia (AML), chronic myelogenous leukemia (CML), acute lymphoblastic leukemia (ALL), or myelodysplastic syndrome (MDS), analysis of donor KIR genotype with HLA genotype demonstrated that 62.9% of the patients lacked an HLA ligand for donor-inhibitory KIR. Lack of HLA ligand for donor-inhibitory KIR (missing KIR ligand) had no effect on disease-free survival (DFS), overall survival (OS), or relapse in patients receiving transplants for CML and ALL. In patients with AML and MDS, however, there was a significant missing KIR ligand effect on DFS (P = .014; hazard ratio [HR], 0.53; 95% confidence interval [95% CI], 0.28-0.88) and OS (P = .03; HR, 0.53; 95% CI, 0.3-0.93). Incidence of relapse was also lower in patients with AML and MDS who lacked the HLA ligand for donor-inhibitory KIR (P = .04; HR, 0.41; 95% CI, 0.18-0.97). AML and MDS patients lacking 2 HLA ligands for donor-inhibitory KIR had the highest DFS (P = .002) and OS (P = .003). There was no significant contribution of donor-activating KIR to transplantation outcome in these patients. These data indicate that the absence of class I ligand in the recipient for donor-inhibitory KIR can be a prognostic factor for transplantation outcome in HLA-identical sibling transplantation and that the lack of HLA-C or -B ligands for donor-inhibitory KIR can contribute to improved outcomes for patients with AML and MDS.     

Reconstitution of NK cell receptor repertoire following HLA-matched hematopoietic cell transplantation

Interactions between killer immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) class I ligands influence development of natural killer (NK) cell repertoire and response to infection, cancer, and allogeneic tissue. As KIRs and HLA class I molecules are highly polymorphic, clinical allogeneic hematopoietic cell transplantation is predicted to frequently involve KIR mismatch, and thus to provide a unique system for study of human NK cell receptor repertoire development. Eighteen leukemia patients undergoing HLA-matched transplantation and their donors were analyzed for KIR genotype. Ten of 13 HLA-identical donor-patient pairs were KIR mismatched and 3 were matched; all HLA-matched unrelated pairs were KIR mismatched. Reconstitution of recipient NK cell repertoire following transplantation was examined using flow cytometry and monoclonal antibodies specific for KIR and CD94:NKG2A. These data form 3 groups. Six to 9 months after transplantation, 8 patients (group 1) reconstituted an NK cell repertoire resembling that of their donor, and for KIR-mismatched transplants, distinct from the recipient before transplantation. In the first year after transplantation, 5 patients (group 2) exhibited a generally depressed frequency of KIR-expressing NK cells and concomitant high frequency of CD94:NKG2A expression. By 3 years after transplantation, the frequency of KIR-expressing NK cells had increased to donor values, in the 3 patients from group 2 analyzed for this period. The remaining 5 patients experienced severe clinical complications following transplantation and displayed unique features in their NK cell receptor reconstitution. These results demonstrate that a majority of HLA-matched hematopoietic cell transplantations involve KIR mismatch and reveal differences in NK cell repertoire having potential impact for immune responsiveness and transplantation outcome.     

Association of KIR3DS1+HLA-B Bw4Ile80 Combination with Susceptibility to Tuberculosis in Lur Population of Iran

Background: Natural killer (NK) cells are the effector cells of innate immunity that respond to infection and tumor. Interactions between killer cell immunoglobulin like receptors (KIR) and human leukocyte antigen (HLA) class I molecules regulate NK cells responses to eliminate infected and transformed cells. Objective: To investigate the impact of KIR genes, HLA ligand genes, and KIR-HLA combinations on susceptibility to tuberculosis (TB) in Lur population of Iran. Methods: The genomic DNA of 50 patients with TB from Lorestan province of Iran was genotyped for sixteen KIR genes and their five major HLA class I ligands were determined by a polymerase chain reaction-sequence-specific primers (PCR-SSP) assay. The results were compared with those of 200 healthy unrelated Iranian individuals. Results: In Lur population of Iran, a significant decrease in frequency of KIR3DS1 was found in TB patients compared to control group (24% vs. 44.5%, OR=0.394, CI=0.194-0.798, p=0.013). Also, among the three activating genes that may use HLA class I molecules as their ligands, a significant decrease was shown in frequency of KIR3DS1 with HLA-B Bw4Ile80 ligand in TB patients compared to control group (4% vs. 23%, OR=0.14, CI=0.033-0.596, p=0.004). Conclusion: These findings imply a genetic imbalance between activating and inhibitory KIR genes and KIR-HLA combinations in Lur TB patients. Low level of activating KIR3DS1 and its combination with HLA-B Bw4Ile80 ligand might have an influence on the susceptibility to TB in Lur population of Iran.     

Does haploidentical transplantation in children with primary immunodeficiencies have the potential to exploit donor NK cell alloreactivity?

Donor potential to exert NK cell alloreactivity has been shown to confer survival advantage in haploidentical hematopoietic cell transplantation for hematological malignancies. We investigated killer immunoglobulin receptor (KIR) ligand incompatibility in 40 children receiving haploidentical transplantation for primary immunodeficiencies. The conditioning regimen consisted of busulfan and cyclophosphamide. T-cell depletion of the graft used complement-dependent lysis or CD34+ selection. Two patients died in the first month. The remaining 38 patients were divided into those with (n=13) and those without (n=25) donor potential to exert NK cell alloreactivity. Engraftment was similar in the two groups (61.5 and 64%, respectively). The incidence of grade II-IV acute graft-versus-host disease (GVHD) tended to be lower in the group with donor potential to exert NK cell alloreactivity, but the difference was not significant. In conclusion, in this series of patients with primary immunodeficiencies, donor potential to exert NK cell alloreactivity was not associated with significant advantages in engraftment and prevention of acute GVHD.