Evidence is emerging that B cells, once thought to fight infection solely by producing antibodies, might also prevent disease without them. In the traditional view, antibodies specific to a bacterium or virus are produced by B cells and maintained against future infection by certain classes of T cells as part of the slow-but-smart ‘adaptive’ immune response. However, it seems that B cells also play an important role in the short-term immediate immune response to pathogens.
Recent research on this expanded B cell function was thought to apply only to bacterial infection, but a paper published today in Immunity suggests it also applies to viral infection. The study demonstrates that mice without adaptive immune systems, whose B cells have been rendered incapable of producing antibodies, nonetheless survive infection by vesicular stomatitis virus (VSV), a pathogen closely related to rabies that attacks the nervous system. They found B cells were producing type 1 interferon signaling protein that prompted macrophages to recognize the virus and destroy it, protecting the body from invasion, all without antibodies.
“B cells are clearly the difference between life and death from this virus, but antibodies are not the reason for this difference,” says senior author Ulrich von Andrian, an immunologist at Harvard Medical School in Boston.
Taken together, the bacterial and viral studies revolutionize how immunologists understand B cells. “These findings are getting a lot of attention, as they should,” says Lyle Moldawer, an immunologist at the University of Florida in Gainesville and the first to publish evidence of an innate B-cell response in bacterial infection. “B cells are the last cell population that anyone considered to be involved in primary response to a viral or bacterial infection.” Moldawer’s August 2011 study was the first to demonstrate that B cells communicating via type 1 interferon contributed to protection against primary infection.
Immunologists are quick to warn that their findings do not undercut the importance of vaccines, which guard against future infection by priming B cells to create antibodies against a particular pathogen. “What we are beginning to understand is an additional function of B cells in preventing infection, not an alternative function,” says von Andrian. However, the additional role of B cells could provide new targets for treating bacterial and viral disease, he says, potentially by boosting the interferon response to protect the body soon after infection.
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