IMMUNOLOGICAL PROPERTIES OF TTT M-87 CELL-LINE ESTABLISHED FROM MURINE PITUITARY TUMOR-ASSOCIATED MACROPHAGES/

TtT/M-87 cell is a macrophage cell line established from thyrotropic p ituitary tumor tissues in mouse. In this paper, we report the immunolo gical properties of M-87 cells as a model of tumor-associated macropha ge. Contrasting with resident peritoneal macrophages, M-87 cells const itutively secreted small but significant amounts of TNF-alpha and IL-l alpha, which were detectable in both biological assays (cytotoxic act ivity for L929 and co-mitogenic activity for Con A-induced T cell prol iferation, respectively) and ELISA, and produced larger amounts of the se cytokines upon stimulation with LPS. They expressed MHC class II mo lecules on their cell surface without stimulation by IFN-gamma. The ac cessory or antigen-presenting cell activity in antibody-producing resp onse of spleen lymphocytes to sheep red blood cells was shown to be mu ch higher in M-87 cells than normal peritoneal macrophages. In additio n, when normal spleen lymphocytes were cultured with allogeneic tumor cells, such as EL-4 and S-180, in the presence of M-87 cells, lymphocy tes reactive to stimulator cells were activated to manifest inhibitory effect on the tumor cell growth and also to manifest specific cytotox ic effect on the allogeneic tumor cells. These results show that M-87 cells derived from tumor-associated tissue are activated macrophages a nd that they are inhibitory to tumor cell growth and augmentative in t he induction of T-cell-mediated immune responses.