In vivo cytotoxic responses induced by allogeneic normal and neoplastic cells in mice: relative lack of immunogenicity of B16 melanoma cells.

It has been previously reported from this laboratory that the C57BL/6 melanoma B16 will grow in allogeneic mice provided that donor-derived passenger leukocytes are first removed by in vitro passage of the tumor cells. In this paper we report that allogeneic and syngeneic mice support similar survival of [125I]iododeoxyuridine-labeled B16 cells (125I-B16 cells) as indicated by whole-body retention of 125I. B16 failed to induce the early cytotoxic response which was induced by semiallogeneic peritoneal cells (PC) and by two other allogeneic tumors (EL4 lymphoma and MC-2 sarcoma). They were nevertheless rapidly destroyed by the response induced by PC or EL4. B16 did show some immunogenicity as indicated by regression of some primary B16 tumors (45% ip and the majority of footpad tumors) and by the slow cytotoxic response to secondary 125I-B16 challenge following preimmunization with live or irradiated B16 cells. An equivalent response was induced by preimmunization with a 100-fold lower dose of PC. These findings are discussed in relation to the requirement for inductive stimuli, in addition to antigen, for the stimulation of in vivo cytotoxic responses.