Microbial Influences

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Science  04 Dec 2009:
Vol. 326, Issue 5958, pp. 1321
DOI: 10.1126/science.326.5958.1321-a

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Filamentous bacteria.

CREDIT: IVANOV ET AL., CELL 139, 485 (2009)

Our guts are colonized by trillions of commensal microbiota, whose influence on our immune systems is just beginning to be appreciated. Altered colonization has been associated with diseases such as allergy and inflammatory bowel disease, suggesting that commensals may play an important role in regulating immune system responses; to what extent, however, is not yet understood.

CREDIT: IVANOV ET AL., CELL 139, 485 (2009)

Gaboriau-Routhiau et al. have addressed this issue by comparing germ-free and normally colonized mice. They found that commensal microbiota were critical for maintaining T cell homeostasis in the gut. Germ-free mice exhibited altered gene expression profiles of cytokines and transcription factors that were associated with T helper cell–mediated immune responses. Recolonization with microbiota derived from mouse fecal matter restored normal expression patterns. Surprisingly, this effect was largely restricted to one strain of bacteria: the segmented filamentous bacteria (SFB). Similar findings were obtained by Ivanov et al., who demonstrated the effects of SFB on interleukin 17–producing T helper cell responses. Thus, these results indicate that T cell immunity is regulated by both host- and microbiota-derived factors and that microbes may actively shape T cell populations in the gut.

Immunity 31, 677 (2009); Cell 139, 485 (2009).

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