Induction of suppressor cell activities in normal lymphocytes by sera from gastric cancer patients.

Inductions of suppressor cell activities in normal lymphocytes by sera from 154 patients with primary gastric cancer were investigated. Sera from patients with advanced cancer induced suppressor cells which significantly depressed the proliferative responses of autologous responder lymphocytes, while those from early cancer did not. An increase in OKT8 reactive T cell populations in normal lymphocytes occurred rather than a decrease in OKT4 reactive T cells after stimulation with sera as well as concanavalin A in relation to the increase of suppressor cell activities. Furthermore, sera-induced suppressor cell activities apparently correlated with spontaneous suppressor cell activities in cancer donors and both of these activities declined after plasma exchange. These results suggest that sera from gastric cancer patients may contain factors which can induce such suppressor cell activities and that serum factors may activate the suppressor precursors to be spontaneous suppressor cells in vivo in a manner similar to that seen in vitro.