The V gene repertoire as revealed by polyclonal B cell activators.

The evidence for the one non-specific signal hypothesis stating that the B lymphocytes are activated by non-clonally distributed receptors which are not the Ig receptors, have been summarized. Even though protein A is a polyclonal B cell activator, it does not exert its effect by interacting with the Fc part of Ig receptors. One consequence of the one non-specific signal concept is that thymus-dependent antigens cannot activate or tolerize B cells. It was shown that B cells from animals tolerant to a thymus-dependent protein antigen could be activated by polyclonal B cell activators to produce antibodies against the tolerogen. Experimentally induced tolerance did not differ from tolerance to self antigens, since LPS and PPD induced autoantibodies capable of lysing autologous red cells and isotope labelled autologous and syngeneic spleen cells. Thus, B cells cannot discriminate self from nonself whereas T cells have been shown to possess this ability.