Delayed or delayed sequential bone marrow transplantation: relevance for acute graft-versus-host disease prevention after major H2 incompatible transplantation.

During this study, BalB/C mice were used as recipients and C57 bl/6 mice as donors. Recipients were given 800 cGys of total body irradiation (TBI) on day 0. Transplantation was carried out as follows: group (1): TBI on day 0; group (2): TBI on day 0 and transplantation on day +1; group (3): TBI on day 0 and transplantation on day 4; group (4): TBI on day 0 and transplantation started from day 4 through day 8. Mice that received TBI only died by day 11. All group 2 mice developed aGVHD and died by day +15. In total, 70% of group 3 were still surviving by day 60 (P<0.001, compared to day +1 transplantation). Survival rates were 90% at day 60 for group 4 (P<0.001 compared to day 1 transplantation). No survival advantage was found between animals transplanted on day 4 and animals with delayed sequential transplantation (P=0.1). Significant engraftment was found in both groups 3 and 4, with no significant differences in the percentages of donor-derived cells between the two groups (P>0.05). These data demonstrate that either delayed or delayed sequential transplantation after TBI can be an effective approach for aGVHD prevention.