OBJECTIVETo study the effect of alloreactive natural killer (NK) cells used in conditioning regimen on elimination of recipient-type T cell and granulocyte, reconstitution of hematopoiesis, engraftment and graft-versus-host disease (GVHD) in murine major histocompatibility complex (MHC) haploidentical bone marrow transplantation (BMT).

METHODSThe murine model of MHC haploidentical BMT was established by using (C57BL/6 x BALB/c) BCF(1) (H-2(d/b)) mouse as the donor, and BALB/c (H-2(d)) mouse as the recipient. Recipient mice were divided into 8.5 Gy control group and 7, 6 and 5 Gy experimental groups according to different irradiation dose and different kinds of NK cell treatment. The control group was further subdivided into untreated and BMT groups, while each experimental group was subdivided respectively into untreated group, BMT group, non-allo-reactive NK cells (non-allo NK) group and alloreactive NK cells (allo NK) group. The effect of adding alloreactive NK cell to conditioning regimen was assessed by peripheral white blood cell and platelet counts, recipient type H-2(d+) T cells and granulocytes counts, expression of H-2(d/b+) cells and pathohistological examination.

RESULTSSurvival time was (6.00 +/- 0.82) days for 8.5 Gy untreated group, and beyond 60 days for all the other groups. No clinical and histopathological evidence of GVHD was observed in all the groups. The reconstitution of hematopoiesis was faster in allo NK groups than in other groups (P < 0.05). On day 1 after BMT, in allo NK groups with different irradiation dose, bone marrow and spleen recipient type H-2(d+) granulocytes and T cells were significantly decreased compared with identical BMT groups and non-allo NK groups (P < 0.05). The engraftment rates of H-2(d/b+) cells were significantly higher in 7, 6 and 5 Gy allo NK groups than in identical BMT groups and non-allo NK groups (P < 0.05, respectively).

CONCLUSIONSIn mouse MHC haploidentical BMT, alloreactive NK cell can eliminate recipient-type T cell and granulocyte, promote reconstitution of hematopoiesis, enhance engraftment while not induce GVHD.