The BMT recipients were inoculated with the “standard” BM (25 × 10⁶)/S (25 × 10⁶) inoculum (A and B) or with an inoculum consisting of 25 × 10⁶ BM cells and varying doses of splenocytes (C), and challenged with “standard” (5 × 10⁶) (A and C) or varying doses of BCL-1 leukemia cells (B). The leukemia burden was determined on day 11 and 23 (A) or 15 and 30 (B and C) after BMT by measuring the spleen weight, histopathologic examination of spleen and liver, and by immunophenotypic analysis of B220⁺ spleen cells (N = 3-6 mice/group), as described in “Materials and methods.” BCL-1 cells were identified as B220⁺H-2D^b− cells. WHI-P131 was used at a dose level of 50 mg/kg per day. P was < .001 for A.2 versus A.1, A.3 versus A.1, A.5 versus A.2, A.6 versus A.2, A.6 versus A.3, B.1 versus A.2, B.3 versus A.2, B.5 versus A.2, B.2 versus A.3, B.4 versus A.3, B.6 versus A.3, C.1 versus A.2, C.3 versus A.2, C.5 versus A.2, C.7 versus A.2, C.2 versus A.3, C.4 versus A.3, C.6 versus A.3, C.8 versus A.3 for both spleen size as well as B220⁺H-2D^b− leukemic BCL-1 fraction of B220⁺ cells in the spleen. There were no statistically significant differences for either the spleen size or the B220⁺H-2D^b− leukemic BCL-1 fraction of B220⁺ splenocytes among any of the subgroups of group B or group C examined at the same time point after BMT. In all allogeneic BMT groups, including A.4, A.5, A.6, and all subgroups of B and C, the spleen size was smaller for mice examined at later time points after BMT. A.4 group mice undergoing allogeneic BMT had larger spleen (P < .001) and fewer B220⁺ splenic B cells (P < .001) than A.1 group mice undergoing syngeneic BMT.