Decreased amounts of antibodies to 22 and 18 kDa antigens in the peritoneal fluid of patients with endometriosis

Accumulated evidence implicates immunological alterations in endometriosis. The purpose of this study was to look for variations in antibodies to distinct antigens in peritoneal fluid of women with and without endometriosis. Peritoneal fluid was aspirated from 17 women undergoing laparoscopy for tubal ligation and 37 patients complaining of symptoms of pain and/or infertility. Peritoneal fluid antibodies to a standard preparation of peritoneal fluid antigens were detected by Western blot analysis using peroxidase-labelled anti-human immunoglobulin G antibodies specific to the Fc region. Antibodies to distinct antigens were quantified by estimating the ratio of the relative optical density between samples and a standard amount of antibodies. Marked changes were found in the antibody detection to two antigens having apparent molecular weights of 22 and 18 kDa. The intensity of the antibody signal was significantly weaker in the peritoneal fluid from endometriosis patients (0.36 ± 0.06 and 0.46 ± 0.06) compared with that in women without endometriosis (0.62 ± 0.08 and 0.75 ± 0.06). It was also weaker in patients without endometriosis presenting with infertility (0.36 ± 0.07 and 0.47 ± 0.08), but only the 18 kDa antigen result was significant. After adjusting for infertility, the P values for the 18 and 22 kDa bands were 0.03 and 0.28 (not significant) respectively in the group of endometriosis patients. These changes were not related to the phase of the menstrual cycle. These data suggest an alteration in the immune response to two distinct antigens in the peritoneal fluid from women with endometriosis and infertility. Further evaluation of these two antigens and their antibodies would be of interest to help understand endometriosis and its associated infertility. Keywords: antibodies/antigens/endometriosis/peritoneal fluid/Western blot analysis