Fig. 2.

Fetal T cells in preterm labor subsets and term gestation. (Upper left panel) Intra-amniotic infection/inflammation-associated preterm labor and birth are accompanied by the activation of conventional CD4+ and CD8+ T cells by microbial products, resulting in the release of pro-inflammatory cytokines. (Upper right panel) A subset of idiopathic preterm labor cases (preterm labor occurring in the absence of clinical intra-amniotic infection/inflammation) are associated with an increased number of activated fetal CD4+ T cells in amniotic fluid together with elevated concentrations of T-cell cytokines. (Lower left panel) In term pregnancy, fetal immunity is skewed toward a tolerant state, as evidenced by an elevated propensity for fetal naïve T cells to differentiate into regulatory T cells (Tregs). (Lower right panel) Fetal T cells in the amniotic cavity express a phenotype similar to that of intra-epithelial lymphocytes in the intestines, suggesting that some T cells in this compartment are derived from the mucosal organs that are in contact with amniotic fluid