Tumor-specific priming and reactivity of the T-cell response in transfer experiments. Specificity of the priming and reactivity of the T-cell response was tested in cross-over transfer experiments using 2 different fibrosarcomas of BALB/c (H-2^d) origin: MethA and CMS5. (A) Antitumor effects against CMS5 fibrosarcoma in [C57BL/6 × BALB/c]F₁ (H-2^b/d) recipients of transplants from either [C57BL/6 × BALB/c]F₁ (H-2^b/d) donors (□, syngeneic control); BALB/c (H-2^d) donors (•, allogeneic model); or C57BL/6 (H-2^b) donors (○, allogeneic model) (n = 5 per group). Mice were subcutaneously inoculated with CMS5 tumor cells on day 14 after transplantation and showed a significantly reduced growth in both allogeneic groups (compare similar experiments with MCA205 and MethA tumor in Figure 1). (B) Weight loss as measure of GvHD was observed in both groups receiving transplants from allogeneic donors and was absent in the syngeneic model. (C) Growth of MethA (H-2^d) tumors in lethally irradiated naive BALB/c (H-2^d) mice after adoptive transfer of spleen cells from non-tumor-bearing (□,n = 10); MethA (•,n = 9), or CMS5-bearing (▴,n = 7) F₁ recipients of transplants from BALB/c donors. Inhibition of MethA tumor growth was observed only after transfer of spleen cells from MethA-bearing primary transplant recipients. (D) Growth of CMS5 (H-2^d) tumors in naive secondary BALB/c recipients after transfer of spleen cells from non-tumor-bearing (□,n = 6), CMS5-bearing (•,n = 5), or MethA-bearing (▴, n = 7) F₁ mice receiving transplants from BALB/c donors. A transferable GvT effect against CMS5 was evident only with spleen cells derived from CMS5-bearing primary transplant recipients. Data are presented as means ± SD. ^*P < .05 versus respective control groups.