The mammalian intestinal mucosa harbors over one trillion microbes, predominantly comprised of bacterial species, which easily surpass the number of host cells. Given this large number and the possible threat of opportunistic infections, the host immune system constantly monitors the epithelial mucosal barriers and regulates microbial interactions at these surfaces. This crosstalk and mutualism established between host and microbe has been heavily researched in recent years. The main efforts have focused on identifying the gut’s role in the formation of a functional immune system, whereas little light has been shed on the specific role of gut bacteria on T cell responses and memory to systemic and local pathogens. Here, we interrogate the role of gut flora on CD4 T cell responses to pathogens by comparing germ-free and specific-pathogen-free mice during systemic (acute LCMV) or localized (oral Listeria monocytogenes) infection as models pathogens. Our results indicate a marked difference between T cell responses in germ-free and specific pathogen free mice, suggesting a role for commensal bacteria not just in shaping the immune system but also in preparing it to respond with effector cells and later sustaining memory cells.
- Copyright © 2013 by The American Association of Immunologists, Inc.