Induction of suppression through human T cell interactions.

Concanavalin A (Con A) activated T cells, devoid of cells bearing Fc receptors for IgG (T - TG) help human B lymphocytes to differentiate into plasma cells (PC) in response to pokeweed mitogen (PWM). PC differentiation is reduced when adult T cells are added to such cultures. The radiosensitivity of suppression and the radioresistance of help enabled us to show that adult T cells include a suppressor-precursor which is activated by irradiated Con A-precultured T cells. Newborn T cells which include active suppressors, are both poor stimulators of suppressor-precursors and poor helpers of B cells. Our results suggest that at least two cells may mediate Con A-induced suppression, one which suppresses directly and is radiosensitive and another which is radioresistant and stimulates suppressor-precursors in a target population of T cells.