Posttransplantation Cy ameliorates GVHD directed against major plus minor histocompatibility antigens.

(A) Lethally irradiated (850 cGy) C57BL/6 × DBA/2 (B6D2; H-2^b/d) F₁ mice received 4 × 10⁶bone marrow cells and 5 × 10⁷ spleen cells from C57BL/6 (H-2^b) donors on day 0. On day +3, mice receiving transplants were left untreated (▵) or received Cy 200 mg/kg intraperitoneally (♦). Moribund mice were killed, and survival was plotted as a function of time after transplantation. (B-D) B6D2 F₁ mice (CD45.1⁻) received transplants on day 0 of 10⁷ bone marrow cells and 5 × 10⁷spleen cells from B6.SJL (H-2^b, CD45.1⁺) donors after conditioning with nothing, with fludarabine 100 mg/kg/day intraperitoneally on days −6 to −2, with 200 cGy TBI on day −1, or with both. On day 3, mice received nothing or Cy 200 mg/kg intraperitoneally. Each treatment group contained 10 animals, except for the group receiving posttransplantation Cy alone (n = 5). Each asterisk indicates that there is a significant difference (P < .01) between the values on either side of the asterisk. (B) Individual weights were recorded on the day of and 4 weeks after transplantation, and the mean (± SEM) percentage of weight change is plotted for each treatment group. (C) Donor T-cell chimerism 2 months after transplantation. (D) Donor myeloid chimerism 2 months after transplantation.