Boston Children's Hospital
Harvard Medical School
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Unlike most tissues in the human body, mucosal surfaces (in particular, the intestine) are colonized by trillions of bacteria.  In healthy individuals, these “commensal” bacteria are not dangerous and provide several benefits to the human host in terms of nutrient metabolism and immune homeostasis.  However, there are instances where the interactions between commensal bacteria and the host result in pathology.  Inflammatory bowel disorders (IBDs), a growing problem in the developed world, are caused by inappropriate innate immune responses to commensal bacteria of the intestine.  Toll-like Receptors (TLRs), and other microbe-detection receptors, have emerged as regulators of IBD, yet there is no clear understanding of their mechanisms of action.  The Kagan lab is interested in understanding how TLRs and other microbe-detection receptors operate within the epithelial cells of the intestine, which are the only human cells in direct contact with the microbes of the gut.