OBJECTIVETo explore the effect of donor-derived NK cells added to pretreatment conditioning regimen on hematopoietic reconstitution after MHC haplotype-mismatched BMT in mice.

METHODSMurine model of MHC haplotype-mismatched BMT was established by using BALB/c(H-2d) x C57BL/6(H-2b) (CB6F(1)(H-2d/b)) mouse as recipient, and C57BL/6(H-2b) mouse as donor. Fifty recipient mice were divided into 5 groups. The mice in the first three groups were each infused 1 x 10(6), 5 x 10(5), 2 x 10(5)/mouse donor-derived NK cells, respectively before TBI ((60)Co, 9.0 Gy) and then conditioned with TBI, followed by infusion of C57BL/6(H-2b) mice bone marrow cells four hours later. The mice in the fourth group received TBI only, and in the fifth group, TBI and BMT at the some doses as the first three groups. Hematopoietic reconstitution, survival time, body weight, histopathology of the recipients were followed up.

RESULTS(1) Survival time was (5.15 +/- 0.66) days for the fourth group, and > 30 days for the other 4 groups. (2) Leukocyte and platelet counts at day 10 after BMT were (0.99 +/- 0.22) x 10(9)/L and (61.0 +/- 7.27) x 10(9)/L respectively for the fifth group and (2.01 +/- 0.21) x 10(9)/L, (101.50 +/- 16.34) x 10(9)/L; (1.98 +/- 0.29) x 10(9)/L, (99.50 +/- 16.41) x 10(9)/L and (1.97 +/- 0.21) x 10(9)/L, (98.0 +/- 16.19) x 10(9)/L for the first three groups, respectively. Histopathology displayed no GVHD in all the groups.

CONCLUSIONDonor-derived NK cells could promote hematopoietic reconstitution after MHC haplotype-mismatched BMT in mice.