Commensal bacteria directly suppress<i>in vitro</i>degranulation of mast cells in a MyD88-independent manner

Abstract

The intestine harbors a substantial number of commensal bacteria that provide considerable benefits to the host. Epidemiologic studies have identified associations between alterations in the composition of the intestinal microbiota and the development of allergic disease. However, the cellular and molecular mechanisms underlying these effects remain to be determined. Here, we show that heat-killed commensal bacteria suppressed degranulation of mast cells in vitro in a MyD88-independent manner. In particular, Enterococcus faecalis showed the strongest suppression of degranulation through partial inhibition of Ca(2+) signaling upon the high affinity IgE receptor (FcεRI) cross-linking.