B-1 cells as a source of IgA

Immunoglobulin A (IgA) is the most abundantly produced immunoglobulin found primarily on mucosal surfaces. The generation of IgA and its involvement in mucosal immune responses have been intensely studied over the past years. IgA can be generated in T cell-dependent and T cell-independent pathways, and it has an important impact on maintaining homeostasis within the mucosal immune system. There is good evidence that B-1 cells contribute substantially to the production of mucosal IgA and thus play an important role in regulating commensal microbiota. However, whether B-1 cells produce antigen-specific or only nonspecific IgA remains to be determined. This review will discuss what is currently known about IgA production by B-1 cells and the functional relevance of B-1 cell-derived IgA both in vitro and in vivo.