FOXP3 and autoimmune disease: CD4+ T regulatory cells (Treg cells), which were formerly defined as suppressor T cells, with the co-expression of the transcriptional regulator forkhead box protein P3 (FOXP3), contribute to modulating the immune system, which includes preserving tolerance to self-antigens, avoiding autoimmune disease, and dynamically enhancing the decidua during embryo implantation and early pregnancy [96], but they seem to be unnecessary for the maintenance of the third trimester pregnancy in humans [97,98,99].