Communication Between the Microbiota and Mammalian Immunity

Mammalian immune systems evolved within a diverse world dominated by microbes, making interactions between these two life-forms inevitable. Adaptive immunity protects against microbes through antigen-specific responses. In classical studies, these responses were investigated in the context of pathogenicity; however, we now know that they have significant effects on our resident microbes. In turn, microbes employ an arsenal of mechanisms to influence development and specificity of host immunity. Understanding these complex reactions will be necessary to develop microbiota-based strategies to prevent or treat disease. Here we review the literature detailing the cross talk between resident microbes with a focus on the specificity of host responses and the microbial molecules that influence them.