IgG B memory cell subpopulations: differences in susceptibility to stimulation by TI-1 and TI-2 antigens

Spleen cells from mice primed with the thymus dependent (TD) antigen trinitrophenyl keyhole limpet hemocyanin several months earlier can be stimulated in vitro to produce an IgG anti-hapten response to TD as well as thymus independent (TI) forms of the hapten. Selective killing of TD or TI-2 responding B cells can be accomplished with the corresponding antigen by bromouridine deoxyribose (BUdR) and light treatment without affecting the other population. In contrast, we show here that selective killing with TI-1 antigens does not occur. Rather, the TI-1 antigens, TNP-Brucella abortus or TNP-lipopolysaccharide, eliminate both TD and TI-2 responding IgG memory B cells. All TNP-responding B cells are similarly eliminated if cultures are challenged simultaneously with TD and TI-2 antigens before BUdR and light but not when they are challenged with either a TD or TI-2 antigen separately. We conclude that IgG memory B cell precursors stimulated to produce anti-TNP by TD or TI-2 forms of the hapten are defined by only two functionally distinct subpopulations and that TI-1 antigens can stimulate both of these populations at least to divide.