Con-A-induced suppressor activity of lymphocytes distinguished by the presence or absence of the Fc receptor.

In the present work we show that concanavalin A (Con A)-activated cells are competent to suppress polyclonal antibody responses induced by different polyclonal B-cell activators. Such an effect does not seem to be mediated by cytotoxic killer cells nor by overactivation, suggesting, therefore, that true suppressor cells are responsible for the phenomenon. The dose of Con A required for induction of these suppressor cells was found to exceed 2 μg/ml. Irradiation of the suppressor cell population abrogated their inhibitory capacity and no evidence of genetic restriction between effector and responding cells was found. Suppression affects cell proliferation, which suggests that, in our system, suppressor cells act directly on antibody-forming cell precursors by halting their proliferation and/or production of antibody.