Graft-versus-tumor (GvT) and graft-versus-host (GvH) activity in tumor-bearing mice after syngeneic or allogeneic bone marrow transplantation (BMT). (A) Growth of MCA205 fibrosarcoma in the syngeneic (negative control) and both allogeneic transplantation models. [C57BL/6 × BALB/c]F₁ (H-2^b/d) mice received transplants from either [C57BL/6 × BALB/c]F₁ (H-2^b/d) donors (▵, syngeneic model); BALB/c (H-2^d) donors (○, allogeneic model); or C57BL/6 (H-2^b) donors (•, allogeneic model) (n = 5 per group). Transplant-recipient mice were inoculated with MCA205 tumor cells of C57BL/6 (H-2^b) origin. (B) Weight loss after BMT as a measure of GvH disease (experiments and symbols as in panel A). (C) Growth of MethA fibrosarcoma (BALB/c [H-2^d] origin) in the syngeneic and both allogeneic transplantation models. [C57BL/6 × BALB/c]F₁ (H-2^b/d) mice received transplants from either [C57BL/6 × BALB/c]F₁ (H-2^b/d) donors (▵, syngeneic model) (n = 8), BALB/c (H-2^d) donors (•, allogeneic model) (n = 8), or C57BL/6 (H-2^b) donors (○, allogeneic model) (n = 7). Transplant-recipient mice were inoculated with MethA tumor cells of BALB/c (H-2^d) origin. Weight loss as measure of GvH activity was absent in the syngeneic model and comparable to the data shown in B in both allogeneic models. (D) Same experiment as in C with additional transfer of splenic T cells from the donor at the day of BMT (n = 5 per group). Note augmented GvT effects in allogeneic transplant recipients in which donor and tumor share the same MHC background (•). Data are presented as means ± SD. The results are representative of at least 3 independent series of experiments. ^*P < .05 for syngeneic donors (▵) versus allogeneic BALB/c and C57BL/6 donors, respectively (•, ○).