To determine the dominant T-cell subtype in infertile endometriosis patients, Koval et al. studied the expression of transcription factors related to differentiation of various subtypes in eutopic endometrial tissues and found increased expression of T-box expressed in T cells (T-bet) and GATA-binding protein 3 (GATA3), the transcription factors involved in Th1 and Th2 differentiation, and decreased expression of forkhead box P3 (Foxp3), which drives Treg differentiation [85]. This evidence concerns the gene FOXP3 and Infertility.