Figure 2.

Potential mechanisms of maternal microbiota, vaginal delivery, breast feeding effects on the fetal/infant immunity. (A) The early microbial colonization in humans is necessary to maintain a balance between maternal and fetal immunity (30). Fetal microbiota, or their molecular signatures, may form mucosal immunity and prepare the tissues for colonization following birth (18). The maternal microbes and their metabolites have impact on immunity development by epigenetic modifications influencing Th1/Th2 balance, production of SCFAs that may induce T-cell activation and modulate IL-10 release, as well as regulation of TLRs (5, 33–35). (B,C) Vaginal delivery assures own mother's vaginal microbiota colonization. Breast feeding with all bioactive factors assures protective role against infections and maintains the mucosal epithelium and the development of the microbiome (36). Moreover, mother-derived active molecules (including immunoglobulins) assure gut homeostasis with regard to the newly colonizing microbiota by regulating the immune system in the GALT and shaping Innate Lymphoid Cell development in the intestine (36). Milk-derived antibodies from the mother's milk support the child with a passive immunity during the infancy (37). Short-chain fatty acids (SCFAs), Toll-like receptors (TLRs), and gut-associated lymphoid tissue (GALT).