INVITRO INDUCTION OF HUMAN SUPPRESSOR T-CELLS BY MYCOBACTERIAL ANTIGENS - BCG ACTIVATED OKT4+ CELLS MEDIATE SUPPRESSION OF ANTIGEN-INDUCED T-CELL PROLIFERATION

Abstract

Peripheral blood mononuclear cells (PBMC), obtained from BCG vaccinated healthy donors, were induced to proliferation BCG for 5 days in vitro. When re-exposed to BCG, they failed to proliferate. They partially retained the ability to respond to concanavalin A (Con A) and allogeneic cells. The addition of graded numbers of such cultured cells to fresh autologous PBMC suppressed their proliferative response to BCG. These suppressor cells could also inhibit the proliferation of fresh cells to other mycobacteria antigens, both in particulate form, i.e. Mycobacterium leprae, or in soluble form, i.e. purified protein derivative (PPD) and SPA30. However, these pre-cultured cells did not inhibit the response of fresh cells to non-specific mitogens, i.e. Con A and alloantigens. The inhibition of the response to non-mycobacterial soluble antigens, i.e. tetanus toxoid (TT) and diphtheria toxoid (DT) varied with little suppression in some individuals and stronger suppression in others. The suppression to BCG was found to be mediated by T cells. Subfractionation of T cells by monoclonal antibodies OKT4 and OKT8 allocated the suppressor cells to the OKT4+ class of T cells. The suppression of the autologous system was quite strong, it was much weaker in allogeneic systems.