Spontaneous and conA-induced suppressor lymphocytes: a comparative study.

Suppressor monocytes, Concanavalin A(ConA)-induced suppressor T cells, and short-lived suppressor lymphocytes have been describe in humans. The present study was performed to evaluate spontaneous suppression in a test system similar to that employed for the demonstration of ConA-induced suppressor cells: Lymphocytes were either stimulated by ConA (= induced suppressor cells) or immediately mitomycin-treated (= spontaneous suppressor cells). Both preparations were tested for their capacity to suppress mitogen-induced proliferation of autologous cells. Depletion of monocytes or B lymphocytes did not affect spontaneous suppression. The active cells were short-lived in vitro. Therefore the net increase in suppressor activity generated by preculture with ConA is in part related to a loss of spontaneous inhibitory activity in the control cultures kept without mitogen. Spontaneous suppressor cell activity was comparable to that of ConA-induced suppressor cells.