Blood
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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. ⋯ 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.
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The clinical course of chronic lymphocytic leukemia (CLL) differs significantly between patients with mutated (M-CLL) and unmutated (U-CLL) immunoglobulin (Ig) variable heavy-chain (V(H)) genes, implying a role for B-cell receptor (BCR) signaling in the pathogenesis of this disease. We have now investigated activation of downstream BCR signaling pathways in U-CLL and M-CLL B cells using soluble anti-IgM (sol-IgM) and immobilized anti-IgM (imm-IgM) antibodies as models for antigenic stimulation. Ligation of the BCR with sol-IgM induced incomplete responses in both CLL subsets, resembling the pattern described for tolerant B cells. ⋯ Stimulation with imm-IgM elicited a more complete BCR signal and significantly prolonged phosphorylation of ERK and Akt, indicating persistent or repetitive BCR signaling. Moreover, this type of stimulation increased the levels of the antiapoptotic protein myeloid cell leukemia-1 (Mcl-1) and protected from chemotherapy-induced apoptosis, whereas induction of apoptosis and down-regulation of Mcl-1 was observed following stimulation with sol-IgM. These data demonstrate that only sustained BCR signaling can promote survival of CLL B cells and indicate that the main difference between CLL with mutated and unmutated V(H) genes may reside in the availability of such stimulation.