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. Author manuscript; available in PMC: 2016 Jul 13.
Published in final edited form as: Clin Immunol. 2015 Jun 30;159(2):122–127. doi: 10.1016/j.clim.2015.05.014

Figure 1. Interactions between the microbiota and the intestinal immune system.

Figure 1

Germ free and prenatal mice (left) contain underdeveloped and reduced numbers of Peyer’s patches and isolated lymphoid follicles (ILF). Colonization of the intestinal tract with a ‘healthy’ microbiota (middle) stimulates the induction and expansion of lymphoid tissues, and the secretion of antimicrobial peptides (AMP) and IgA. Colonization with inflammatory commensals (right), which are often located within normally sterile sites (such as the inner mucus layer) and induce strong IgA responses, induces chronic inflammatory responses that are characterized by an influx of inflammatory cells such as Th17 and Th1 T cells, inflammatory monocytes and neutrophils.