Selective effects of cyclosporin A on functional B cell subsets in the mouse.

Cyclosporin A, an immunosuppressive peptide of fungal origin, was believed to selectively affect T lymphocyte functions and to have minimal affects on B lymphocytes. This study shows that, in the mouse, T-dependent B cells and those responding to certain T-independent antigens (so-called TI-1 antigens) are indeed resistant to the drug. However, B cells responsive to other TI antigens (TI-2) are exquisitely sensitive. Thus, doses of the drug that completely abrogate responses to dinitrophenylated (DNP) Ficoll or dextran enhance the response to DNP-lipopolysaccharide and have minimal effects on the response to DNP-Brucella abortus. Virgin T helper cells are sensitive to the drug, whereas primed T cells are not. Cyclosporin A sensitivity therefore represents a novel marker of functional B cell subsets in the mouse and presumably points to fundamental physiologic differences between such subsets.