Suppression of the polyclonal B-cell response to lipopolysaccharide by concanavalin-A-treated non-T cells in vitro.

Concanavalin A (Con A), a T-cell mitogen, dose-dependent suppressed the polyclonal antibody response of a purified B-cell population to lipopolysaccharide (LPS) in vitro. This suppression can be attributed to a role of suppressor cells generated in B-cell cultures in response to relatively high doses of Con A. The suppressor cells can be produced in cultures of normal as well as athymic nude spleen cells deprived of plastic-adherent cells and Thy 1.2 positive cells. The suppressing activity of Con-A-treated cells was not abolished by pre-treatment of the cells with anti-Thy 1.2, anti-Lyt 1.1, anti-Lyt 1.2 or anti-Lyt 2.2 serum and complement, and was decreased partially by treatment with anti-Ig serum and complement. Moreover, the suppressing activity was partially decreased by using petri dishes coated with IgG of F(ab')2 fraction of anti-mouse immunoglobulins. Thus, the suppressor activity of Con-A-treated cells was mediated by a non-T cell, possibly a B cell. A role for macrophages was unlikely, but not formally ruled out. The suppressor cells retarded development of polyclonal antibody production by B cells to LPS only when added at the start of culture and was resistant to treatment with anti-mitotic doses of irradiation and mitomycin C. It is possible that the suppressor cells of a B-cell nature play a role in the regulation of excessive B-cell proliferation during antibody responses.