Use of silica to identify host mechanisms involved in suppression of established Friend virus leukemia.

Silica, an agent predominantly toxic for macrophages, inoculated i.v. to Friend leukemia virus (FLV)-infected mice, blocks the FLV-leukemosuppressive effects of chlorite-oxidized oxyamylose (COAM)-statolon treatment. FLV-infected, COAM-statolon-treated mice that have received silica and have failed to suppress FLV leukemia produced normal amounts of interferon, but did not make antibodies cytotoxic for FLV leukemic cells. Transfer of untreated spleen cells, splenic T cells, or thymocytes from mice with suppressed FLV erythroleukemia to FLV-infected mice treated with silica and COAM-statolon restores the humoral immune response to FLV antigens and results in leukemosuppression. Thus, T lymphocytes from mice with suppressed erythroleukemia participate in FLV leukemosuppression either directly as effector cells, or indirectly as helper cell in the production of antibodies to FLV antigens.