The establishment of a relevant regulatory T cell (Treg) pool in the periphery is of importance to ensure immune homoeostasis. Finely tuned signaling pathways in Tregs control the immune response during extreme endocrine changes in pregnancy and afterward. In this study, we investigate the population of Tregs and, in particular, the natural Tregs (nTregs) in healthy women divided into three groups according to the number of previous pregnancies, if any (Gr.1-one pregnancy, Gr.2-≥2 pregnancies, and Gr.0-no pregnancy). The overall analysis showed similar proportions in the entire Treg pool and nTregs (FoxP3+CD45RA+) in all the three groups (p > 0.05). However, the age-related trend of CD25+ nTregs was found to be different in parous and nonparous women. Analysis of phosphorylated ERK1/2, an important signaling molecule in T cell maintenance, showed a significantly higher percentage in CD25+ nTregs in the group of nonparous compared with parous women (p < 0.05). Thus, our results provide evidence that pregnancy may exert a long-lasting impact on the subset of nTregs due to the extreme changes in the hormonal status, which in turn, influences pre- and post-thymic maturation.
Keywords: CD25; ERK1/2; Tregs; nTregs; pregnancy.