Contact dependent suppression of CD4 T cell activation and proliferation by B cells activated through IgD cross-linking.

Although the co-stimulatory interaction between B and T cells is well defined, recent evidence suggests that B cells also have a regulatory role. Here, we show that B cells activated using anti-IgD conjugated to dextran (alpha-delta-dex) directly inhibit T-cell receptor-induced CD4 T-cell activation, proliferation and cytokine production. This effect was observed in CD4 T cells activated both with and without CD28 co-stimulation. T-cell viability was unaffected, and the T-cell suppressive effect was mediated by contact with IgD-activated purified B cells and not by interleukin-10 or other soluble factors. This is the first evidence of IgD-activated B cells mediating inhibition of activation and proliferation of CD4 T cells in humans.