We analyzed 112 patients with high-risk acute myeloid leukemia (61 in complete remission CR; 51 in relapse), who received human leukocyte-antigen (HLA)–haploidentical transplants from natural killer ...(NK) alloreactive (n = 51) or non-NK alloreactive donors (n = 61). NK alloreactive donors possessed HLA class I, killer-cell immunoglobulin-like receptor (KIR) ligand(s) which were missing in the recipients, KIR gene(s) for missing self recognition on recipient targets, and alloreactive NK clones against recipient targets. Transplantation from NK-alloreactive donors was associated with a significantly lower relapse rate in patients transplanted in CR (3% versus 47%) (P > .003), better event-free survival in patients transplanted in relapse (34% versus 6%, P = .04) and in remission (67% versus 18%, P = .02), and reduced risk of relapse or death (relative risk versus non-NK-alloreactive donor, 0.48; 95% CI, 0.29-0.78; P > .001). In all patients we tested the “missing ligand” model which pools KIR ligand mismatched transplants and KIR ligand-matched transplants from donors possessing KIR(s) for which neither donor nor recipient have HLA ligand(s). Only transplantation from NK-alloreactive donors is associated with a survival advantage.
NK cells use a variety of receptors to detect abnormal cells, including tumors and their metastases. However, in the case of melanoma, it remains to be determined what specific molecular interactions ...are involved and whether NK cells control metastatic progression and/or the route of dissemination. Here we show that human melanoma cell lines derived from LN metastases express ligands for natural cytotoxicity receptors (NCRs) and DNAX accessory molecule-1 (DNAM-1), two emerging NK cell receptors key for cancer cell recognition, but not NK group 2 member D (NKG2D). Compared with cell lines derived from metastases taken from other anatomical sites, LN metastases were more susceptible to NK cell lysis and preferentially targeted by adoptively transferred NK cells in a xenogeneic model of cell therapy. In mice, DNAM-1 and NCR ligands were also found on spontaneous melanomas and melanoma cell lines. Interference with DNAM-1 and NCRs by antibody blockade or genetic disruption reduced killing of melanoma cells. Taken together, these results show that DNAM-1 and NCRs are critical for NK cell-mediated innate immunity to melanoma cells and provide a background to design NK cell-based immunotherapeutic strategies against melanoma and possibly other tumors.
T cells that accompany allogeneic hematopoietic grafts for treating leukemia enhance engraftment and mediate the graft-versus-leukemia effect. Unfortunately, alloreactive T cells also cause ...graft-versus-host disease (GVHD). T cell depletion prevents GVHD but increases the risk of graft rejection and leukemic relapse. In human transplants, we show that donor-versus-recipient natural killer (NK)-cell alloreactivity could eliminate leukemia relapse and graft rejection and protect patients against GVHD. In mice, the pretransplant infusion of alloreactive NK cells obviated the need for high-intensity conditioning and reduced GVHD. NK cell alloreactivity may thus provide a powerful tool for enhancing the efficacy and safety of allogeneic hematopoietic transplantation.
OBJECTIVES—Atherosclerosis may be caused by increased endothelial damage and by a consumptive loss of endothelial repair capacity by endothelial progenitors. Arterial stiffness is a reliable marker ...of atherosclerosis and a positive correlate of endothelial damage. We investigated whether an increased ratio of CD31/CD42 microparticles to endothelial progenitors, a possible indicator of endothelial damage and impaired endothelium reparation, may contribute to aortic stiffness in hypercholesterolemia. We also studied the in vitro effect of microparticles from hypercholesterolemic patients on endothelial progenitor survival.
METHODS AND RESULTS—Circulating CD31/CD42 microparticles, endothelial progenitors, and aortic pulse wave velocity (aPWV), a measure of aortic stiffness, were measured in 50 patients with never-treated hypercholesterolemia and 50 normocholesterolemic controls. Hypercholesterolemic patients had more circulating CD31/CD42 microparticles, less endothelial progenitors, and a stiffer aorta than controls. aPWV was associated with CD31/CD42 microparticles (r=0.61; P<0.001), endothelial progenitors (r=−0.45, P<0.001), and with cholesterol levels (r=0.51; P<0.001). High plasma cholesterol and a high ratio of CD31/CD42 microparticles to endothelial progenitors independently predicted an increased aPWV. Microparticles from hypercholesterolemic patients caused a significant endothelial progenitor loss in vitro.
CONCLUSIONS—Hypercholesterolemia-related aortic stiffness is promoted by plasma cholesterol directly, increased endothelial damage, and reduced endothelium repair capacity by endothelial progenitors.
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.
NK cells are primed to kill by several activating receptors. Killing of autologous cells is prevented as NK cells co-express inhibitory receptors for self-MHC class I molecules. Human NK cells ...discriminate between different allelic forms of MHC molecules via killer cell immunoglobulin-like receptors (KIRs), which are clonally distributed, and each cell in the repertoire bears at least one receptor that is specific for self-MHC class I molecules. Consequently, when faced with mismatched allogeneic targets, NK cells in the repertoire will sense the missing expression of self-MHC class I alleles and will mediate alloreactions. Recent studies in murine transplant models and data from mismatched haematopoietic transplant trials demonstrate MHC class I mismatches, which generate an alloreactive NK-cell response in the graft-versus-host direction, eradicate leukaemia, improve engraftment and protect against T-cell-mediated graft-versus-host disease.
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.
Inhibitory killer cell immunoglobulin receptors (KIR) bind to major histocompatibility complex antigens. Concise knowledge of KIR ligands allows prediction of natural killer (NK)–cell alloreactivity ...after hematopoietic stem cell transplantation. KIR3DL1 binds to the Bw4 epitope on HLA-B antigens. Although the same epitope is also found on 4 HLA-A antigens (HLA-A23/24/25/32), these are not currently regarded as KIR3DL1 ligands. We show that expression of HLA A*2301, A*2402, or A*3201 but not HLA A*2501 protects target cells from lysis by KIR3DL1+ NK cells. KIR3DL1+ NK cells from donors expressing the Bw4 epitope on an HLA-A antigen only are fully functional and capable of lysing Bw4− target cells. HLA A25 differs at amino acid 90, close to the serologic Bw4 epitope, from A23/24/32 and from Bw4+ HLA-B antigens. These data suggest that HLA-A antigens should be taken into consideration when assessing the potential for NK alloreactivity after hematopoietic stem cell transplantation.
Inhibitory-cell killer immunoglobulin-like receptors (KIR) negatively regulate natural killer (NK) cell–mediated killing of HLA class I–expressing tumors. Lack of KIR-HLA class I interactions has ...been associated with potent NK-mediated antitumor efficacy and increased survival in acute myeloid leukemia (AML) patients upon haploidentical stem cell transplantation from KIR-mismatched donors. To exploit this pathway pharmacologically, we generated a fully human monoclonal antibody, 1-7F9, which cross-reacts with KIR2DL1, -2, and -3 receptors, and prevents their inhibitory signaling. The 1-7F9 monoclonal antibody augmented NK cell–mediated lysis of HLA-C–expressing tumor cells, including autologous AML blasts, but did not induce killing of normal peripheral blood mononuclear cells, suggesting a therapeutic window for preferential enhancement of NK-cell cytotoxicity against malignant target cells. Administration of 1-7F9 to KIR2DL3-transgenic mice resulted in dose-dependent rejection of HLA-Cw3–positive target cells. In an immunodeficient mouse model in which inoculation of human NK cells alone was unable to protect against lethal, autologous AML, preadministration of 1-7F9 resulted in long-term survival. These data show that 1-7F9 confers specific, stable blockade of KIR, boosting NK-mediated killing of HLA-matched AML blasts in vitro and in vivo, providing a preclinical basis for initiating phase 1 clinical trials with this candidate therapeutic antibody.
Aspergillus and cytomegalovirus are major causes of morbidity/mortality after haploidentical hematopoietic transplantation. The high degree of mismatching makes cell immunotherapy impossible as it ...would result in lethal graft-versus-host disease (GvHD). We generated large numbers of donor T-cell clones specific for Aspergillus or cytomegalovirus antigens. We identified clones potentially responsible for causing GvHD by screening them for cross-reactivity against recipient mononuclear cells. Nonrecipient reactive, pathogen-specific clones were infused soon after transplantation. They were CD4+ and produced high levels of interferon-γ and low levels of interleukin-10. In 46 control transplant recipients who did not receive adoptive therapy, spontaneous pathogen-specific T cells occurred in low frequency 9 to 12 months after transplantation and displayed a nonprotective low interferon-γ/high interleukin-10 production phenotype. In the 35 recipients who received adoptive therapy, one single infusion of donor alloantigen-deleted, pathogen-specific clones in the dose range of 105 to 106 cells/kg body weight did not cause GvHD and induced high-frequency T-cell responses to pathogens, which exhibited a protective high interferon-γ/low interleukin-10 production phenotype within 3 weeks of infusion. Frequencies of pathogen-specific T cells remained stable over time, and were associated with control of Aspergillus and cytomegalovirus antigenemia and infectious mortality. This study opens new perspectives for reducing infectious mortality after haploidentical transplantations.
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