CELL-MEDIATED IMMUNE-RESPONSE INVITRO .2. MECHANISM(S) INVOLVED IN SUPPRESSION OF DEVELOPMENT OF CYTOTOXIC LYMPHOCYTES

Abstract

Spleen cells [mouse] harvested from mixed leukocyte cultures (MLC) on day 2 or 3 suppress the development of CL [cytotoxic lymphocytes] from a fresh MLC across a cell-impermeable membrane. Day 4 MLC cells, which have the maximum level of CL, showed only a limited effect. Inhibition was observed only when suppressor cells were restimulated with the same H-2 type cells used during induction. The suppressive effect was not strain specific; i.e., CBA-induced C57BL/6 spleen cells effectively inhibited the development of CL from DBA/2-induced C57BL/6 cells. DBA/2-induced C57BL/6 spleen cells effectively inhibited the development of CL from CBA cells. B10 spleen cells stimulated by B10.D2 cells gave rise to a suppressor cell population, indicating that H-2 differences alone can induce the response. The suppressive effect seemed to be exerted on an early phase of the response since no detectable inhibition was observed when suppressor cells were added 48 h after culture initiation. The suppressive effect is not exerted on the accessory cell function but seems to inhibit DNA synthesis of the reacting cells in the MLC.