Researchers have identified the cells responsible for rapid delivery of blood-borne antigens to specialized sites in the spleen. These antigens are derived from pathogens that have invaded the bloodstream and immune responses are initiated once they reach the spleen. The findings are reported online in Nature Immunology.
The immune cells, called marginal zone B cells, reside in the spleen and are constantly bathed in blood. Previous work identified these cells as first responders for making antibodies to bacteria or other pathogens that may have invaded the bloodstream. However, such cells were previously considered immobile and their response, although rapid, was thought not to involve other cells of the immune system and thus weaker than subsequent immune responses that develop deeper within the spleen in sites called follicles. This situation posed a problem as to how the follicular immune cells would encounter such antigens.
Jason Cyster and colleagues show that these marginal zone B cells capture antigens from the blood and, like a courier service, deliver packets of antigen to follicular immune cells. The marginal zone B cells then race back to the blood-rich marginal sinuses to capture more antigen. By inhibiting chemical cues that direct traffic in the spleen, the authors reveal this 'shuttle' service displayed by the marginal zone cells. Such a delivery service ensures an efficient and rapid mode of eliciting strong immune responses to invaders present in the bloodstream.
Jason Cyster (University of California San Francisco, CA, USA)
Abstract available online.
(C) Nature Immunology press release.
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