miRNA Regulation of Immune Tolerance in Early Pregnancy.

To support embryo implantation, the female reproductive tract must provide a tolerogenic immune environment. Seminal fluid contact at conception contributes to activating the endometrial gene expression and immune cell changes required for robust implantation, influencing not only the quality of the ensuing pregnancy but also the health of offspring. miRNAs are small non-coding RNAs that play important regulatory roles in biological processes, including regulation of the immune environment. miRNAs are known to contribute to gene regulation in pregnancy and are altered in pregnancy pathologies. Recent studies indicate that miRNAs participate in establishing immune tolerance at conception, and may contribute to the regulatory effects of seminal fluid in generating tolerogenic dendritic cells and T regulatory cells. This review highlights those miRNAs implicated in programming immune cells that are critical during the peri-conception period and explores how seminal fluid may regulate female tract miRNA expression following coitus.