IgG2a is known to be the most efficient antibody isotype for viral clearance. Here we demonstrate a novel pathway of B cell activation, leading to IgG2a production, and involving synergistic stimulation via B cell antigen receptors, TLR7 and interferon-gamma receptors. This leads to induction of T-bet expression in B cells, driving their differentiation into age-associated B cells (ABCs). T-bet positive ABCs appear during anti-viral responses and produce high titers of anti-viral IgG2a antibodies which are critical for efficient viral clearance. The results thus demonstrate a previously unknown role for T-bet expression in B cells during viral infections. Moreover the appearance of ABCs during anti-viral responses and during autoimmunity suggests a possible link between these two processes.
- Copyright © 2013 by The American Association of Immunologists, Inc.