Retroviral help for B cells

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Science  19 Dec 2014:
Vol. 346, Issue 6216, pp. 1454-1455
DOI: 10.1126/science.aaa3263

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Endogenous retroviruses are footprints left by past retroviral infections that have incorporated viral elements into our genomes (1). They constitute an important component of our virome, the collective genomes from viruses peacefully inhabiting our body (2). These viruses are part of a larger community of commensal and symbiotic microorganisms. The most studied members of this microbiota are commensal bacteria colonizing mucosal organs, including the gut (3). Besides breaking down food and generating nutrients, gut commensals impede the growth of pathogens and stimulate immune system development, including the production of antibodies by intestinal and systemic B cells (4, 5). On page 1486 of this issue, Zeng et al. (6) show that endogenous retroviruses can also mobilize B cells to rapidly produce antibodies against pathogenic antigens.

Protein antigens usually elicit antibody production by B cells through a T cell–dependent pathway that involves B cell–T cell interaction in lymphoid follicles (7). Engagement of the B cell receptor (BCR) by discrete protein epitopes, as well as the production of B cell–stimulating factors by T cells, trigger the differentiation of follicular B cells into long-lived memory B cells and plasma cells that produce protective immunoglobulin G (IgG) antibodies (8).