CD8A and endometriosis: On one hand, some studies have been focused on downregulation of anti-endometrial implants cells, such as NK cells, CD4+/CD8+ T cells, B cells and so on [5–8], on the other hand, some studies demonstrated that increased immunosuppressive cells could promote the progression of endometriosis, such as Tregs (regulatory T cells), TH2 (T helper) cells and even MDSCs (myeloid derived suppressor cells), which have been suggested recently to promote the implantation of endometrial tissue [13, 14].