Many studies have also evaluated the role of immune activation in women with endometriosis (i.e., bcl- and bax-gene activation in PF macrophages); however, only a few studies have dealt with the issue of macrophage apoptosis in endometriosis and have assessed Fas antigen expression on PF macrophages in the disease [37, 38]. The gene discussed is FAS; the disease is endometriosis.