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Immune-mediated processes are considered important in the pathogenesis of bone marrow failure syndromes (BFS). We previously reported that natural killer group 2D (NKG2D) ligands were expressed on pathological blood cells of patients with BFS and that NKG2D immunity may be involved in bone marrow failure. In addition to membranous NKG2D ligands on the cell surface, soluble NKG2D ligands can exist in plasma. We therefore examined the relationship between soluble NKG2D ligands and blood cell counts in 86 patients with BFS, including aplastic anemia, myelodysplastic syndrome with single lineage dysplasia, and paroxysmal nocturnal hemoglobinuria. Approximately half of the BFS patients were positive for soluble NKG2D ligands in the plasma by enzyme-linked immunosorbent assay, and soluble NKG2D ligand-positive BFS patients exhibited severe cytopenia regardless of membranous NKG2D ligand expression. In vitroanalyses demonstrated that soluble ULBP1, an NKG2D ligand, down-regulated NKG2D receptors on CD2-positive cells in peripheral blood. Moreover, soluble ULBP1 attenuated the cytotoxic effects of peripheral blood mononuclear cells on K562, which express membranous ULBP1. Our results suggest that soluble NKG2D ligands can be easy-to-measure biomarkers for the prediction of activity of immune-meditated bone marrow injury in BFS and that soluble NKG2D ligands suppress redundant immune-mediated bone marrow injury.

t(8;22)(p11;q11) is a rare but recurrent chromosome translocation that has been reported in 11 cases of myeloproliferative neoplasm or B-acute lymphoblastic leukemia. This translocation results in an in-frame fusion of FGFR1 on 8p11 and BCR on 22q11, and causes constitutive activation of the tyrosine kinase of the BCR/FGFR1 chimera protein. Here, we report the twelfth case of hematological tumor bearing t(8;22)(p11;q11). The bone marrow showed hypoplastic and tri-lineage dysplasia with 24.4% abnormal cells. The abnormal cells were not defined as myeloid or lymphoid morphologically, lacking a myeloperoxidase reaction. Flow cytometric analysis of the bone marrow cells revealed that the abnormal cells expressed CD13, CD33, CD34, and CD19, and that a fraction of the abnormal cells was positive for CD10. Southern blot analysis of the bone marrow cells showed rearrangement of the immunoglobulin heavy chain gene, a genetic hallmark of B-cell differentiation. Previously reported cases with t(8;22)(p11;q11) suggested an association between myeloid and B-lymphoid tumors, whereas other chromosome translocations involving FGFR1 on 8p11 showed a link between myeloid and T-lymphoid tumors. Our observation supports that t(8;22)(p11;q11) might define a dual myeloid and B-lymphoid disorder.