The prevalence of endometrial immunoglobulin G antibodies in patients with endometriosis

The purpose of this study was to investigate the frequency of antibodies in the serum of patients with endometriosis reacting with endometrial, ovarian, thyroid and skeletal muscle antigens. A total of 55 fertile patients with pelvic pain who had endometriosis diagnosed by laparoscopy and confirmed by histology formed the study group, while 43 fertile patients without pelvic pain and undergoing tubal sterilization formed the control group. Eutopic endometrial membrane antigen was prepared from biopsies taken from patients or controls by an ultracentrifugation technique and used in an enzyme-linked immunosorbent assay (ELISA) for immunoglobulin (Ig) G, IgA and IgM endometrial antibodies. Ovarian, thyroid and skeletal muscle antigens were prepared similarly and used in an ELISA. There was a significant difference in the prevalence of IgG antibodies to eutopic endometrial antigens derived from either control or endometriosis patients (P < 0.05). IgA or IgM antibodies against endometrial antigens were not detected. Endometrial antibodies were detectable in both the luteal and the follicular phases of the menstrual cycle. Immunoblot analysis demonstrated the presence of endometrial antigens with molecular weights of 60 and 66 kDa in the eutopic endometrium of patients with endometriosis. Antibodies to thyroid, ovary or skeletal muscle were not detected in these patients. These findings indicate that endometrial antibodies of the IgG class can be detected in approximately 50% of patients with endometriosis but it remains unclear whether these represent a pathologically distinct subgroup of such patients.