Alloantigen-activated lymphocytes from mice bearing a spontaneous "nonimmunogenic" adenocarcinoma inhibit its growth in vivo by recruiting host immunoreactivity.

Nylon wool columns eluting lymphocytes from the spleen of mice bearing a clinically evident spontaneous, nonimmunogenic adenocarcinoma of recent origin (TS/A) do not display cytotoxic response, release of lymphokines, and proliferation in vitro against TS/A cells, nor do they inhibit TS/A tumor growth in a Winn-type neutralization assay in vivo. After 5-day co-culture with allogeneic spleen cells from mice differing at multiple minor histocompatibility antigens only, these lymphocytes are still noncytolytic against TS/A cells, whereas they release interferon-gamma, mediate delayed-type hypersensitivity (DTH) reactions, and inhibit TS/A tumor growth in the Winn assay. In the Winn test, alloactivated lymphocytes from TS/A tumor-bearing mice are more effective than those from normal mice on a per cell basis. The induction of this TS/A tumor inhibition ability depends on the presence in the cultures of Thy-1+ lymphocytes. The presence of Lyt-2+ lymphocytes is also important, whereas that of asialo GM1+ is not. The TS/A inhibition in vivo by alloactivated lymphocytes mostly depends on Thy-1+, Lyt-2- and asialo GM- lymphocytes, even though a few Thy- cells are also very efficient tumor inhibitors. The alloactivated lymphocytes inhibit TS/A tumor growth by recruiting the radiosensitive effector mechanisms of the recipient mice required for ultimate tumor rejection. TS/A tumor rejection leaves a specific DTH and an immunologic memory resulting in rejection of a second lethal TS/A challenge in a significant number of mice.