Selective Commensals Induce Interleukin-1β in Inflammatory Monocytes to Promote Intestinal Inflammation Aug. 3 (WED) 12:00 / Auditorium (1F), PBC Sang-Uk Seo Seoul National University College of Medicine The microbiota stimulate inflammation, but the signaling pathways and the members of the microbiota involved remain poorly understood. Microbiota induce interleukin-1b (IL-1b) release upon intestinal injury and this is mediated via the NLRP3 inflammasome. Enterobacteriaceae and in particular the pathobiont Proteus mirabilis, induced robust IL-1b release that was comparable to that induced by the pathogen Salmonella. Upon epithelial injury, production of IL-1b in the intestine was largely mediated by intestinal Ly6Chigh monocytes, required chemokine receptor CCR2 and was abolished by deletion of IL-1b in CCR2+ blood monocytes. Furthermore, colonization with P. mirabilis promoted intestinal inflammation upon intestinal injury via the production of hemolysin which required NLRP3 and IL-1 receptor signaling in vivo. Thus, upon intestinal injury, selective members of the microbiota stimulate newly recruited monocytes to induce NLRP3-dependent IL-1b release which promotes inflammation in the intestine. Inquiry: Dr. Sin-Hyeog Im (279-2356) or AIM Administrative Team (Tel.279-8628, E-mail: varsha@ibs.re.kr)