Inhibition of IgG1 and IgE production by stimulation of the B cell CTLA-4 receptor.

Although a large amount of information is available on the activity of CTLA-4 in T cells, the role of this receptor in B cells has not been previously characterized. Our results show that CD40 or LPS stimulation in the presence of IL-4 induces CTLA-4 expression in purified B cells; the maximum level is reached in both membrane and intracellular compartments after 48-72 h. Engagement of the B cell CTLA-4 by immobilized mAb inhibits IgG1 and IgE production and reduces the frequency of IgG1- and IgE-expressing B cells. Cepsilon and Cgamma(1) germline mRNA expression as well as NF-kappaB and STAT6 activation, events required for isotype switching, are also inhibited by CTLA-4 engagement. Together these findings show the critical role of CTLA-4 in the control of IL-4-driven isotype switching and suggest new approaches for modulating immediate-type hypersensitivity responses.