Although the concentration of peritoneal sPD-1 and sHLAG has good diagnostic accuracy, it is less likely to be used widely as less invasive biomarkers are preferred in clinical settings. Abramiuk et al. studied the expression of CTLA4 on the surface of T and B lymphocytes and determined the concentration of sCTLA4 antigen in peripheral blood plasma and peritoneal fluid in patients with endometriosis-related infertility. The gene discussed is CTLA4; the disease is endometriosis.