Figure 3.

Vaginal microbiota and immunity. (A) The vaginal microbiota in a healthy individual is dominated by Lactobacillus spp. The Lactobacillus spp. produce lactic acid as well as antimicrobial compounds to control the growth of microbes. Other soluble factors, such as antimicrobial peptides (AMPs), mannose-binding lectins (MBLs), and immunoglobulins (Igs), contribute to the homeostatic immunity of the vaginal surface. In addition, the surveillance of commensals and pathogenic microbes is achieved by pattern recognition receptors (PRRs). (B) In cases of disrupted vaginal microbiota, such as bacterial vaginosis, community state type IV type microorganisms dominate to initiate an inflammatory response. Short-chain fatty acids produced by these microorganisms are likely to induce the production of proinflammatory cytokines. IL-33 has recently been identified as the key cytokine in association with antiviral immunity modulation by the vaginal microbiome. IL-33 is also responsible for the Th2-type immune response elicited by proteases that are secreted by pathogenic microbes.