Tumor acceptance modified by passage in hybrids with graft-versus-host reaction.

A graft-versus-host reaction (GVHR) was produced in adult F1 hybrid mice by the injection of 10(8) parental strain spleen cells and 8 days later they were challenged with allogeneic third-party tumor. BALB/c Leydig cell tumor (C4092), C57BL/6 sarcoma (30795), and DBA/1 melanoma (S91) often grew progressively in B6D1F1, CD1F1, B6CF1 or their reciprocal hybrid recipients, respectively, when GVHR had been induced in these animals. Control, without GVHR, hybrids always rejected the tumor. The C4092 tumor was serially transplantable in untreated hybrids after its initial passage in unrelated GVHR-treated mice; the S91 grew in its first passage into untreated B6CF1 mice but thereafter was rejected by these hybrids; while the B6 tumor 30795 grew progressively only in the initial GVHR-treated CD1F1 or reciprocal hybrids. Reduced immunogenicity of tumors resulting from passage in unrelated recipients immunosuppressed in association with a GVHR is comparable to allograft adaptation achieved by such techniques as organ culture pretreatment and presents an additional method for attenuating rejection of allotransplants.