Endometrial autoantigens eliciting immunoglobulin g (igG) and igM responses in the sera of baboons with endometriosis

Abstract

The presence of antiendometrial antibodies in the sera of women with endometriosis has been reported by several investigators using various methodologies. Some studies suggest that circulating and peritoneal fluid antibodies involved in immune responses in endometriosis are directed against distinct endometrial antigens, while others failed to detect these. variations in methodology used have been suggested as possible causes of false negative results. The present study was carried out in the baboon, an animal that has been recently developed as a model for research in endometriosis. The presence of specific antibodies against endometrial antigens in this animal has not been reported. Endometrial biopsies were obtained from healthy adult baboons of proven fertility during the luteal phase of the baboon menstrual cycle. A protein extract of the endometrial tissue was separated by electrophoresis on a 12.5-%.polyacrylamide gel. Sera was obtained from 56 baboons (43 with endometriosis and 13 healthy controls without endometriosis). All the sera were tested for IgG antibodies while only serum from 4 healthy controls and 14 animals,with endometriosis were tested with IgM antibodies against endometrial proteins using standard Antibodies of the IgG class present in baboon sera recognized several endometrial antigens but individual variation was evident. No single specific antigen was recognized in baboons with endometriosis. However, sera obtained from baboons with endometriosis demonstrated a statistically significant (p=0.05) higher number of endometrial antigens (9.2±4.5) when compared with the controls (5.2±3.5). A positive correlation was found to exist between number of endometrial antigens and severity of disease. The average number of antigens was 7.9±4.4 (n=25) and 10.9±4.1 (n=18) in stages 1/11, and III/IV respectively. When compared to IgG, sera IgM binding was directed against a relatively small number of endometrial antigens in baboons at different stages of endometriosis. The IgM antibodies recognized distinct antigens with molecular weights of 12 (57%), 50 (29%), and 56 (21%) kilodaltons (KD) and these were restricted to baboons with endometriosis. The 50 and 56 KD antigens were restricted to stage III/IV disease (66.6% and 50% respectively) while recognition of the 12 KD antigen increased with severity of the disease (37.5% in stages I/II versus 83% in stages

Furthermore, another batch of three antigens of , molecular weights 14(42%), 16(43%)' and 58(57%) KD were also present in the baboons; being more prominent in animals with endometriosis (less than 25% in normal animals). The occurance of the 14 and 16 KD antigens also correlated with the severity of the disease (83% in stage III/IV disease versus 13% in stage 1/11 disease). The number of antigens recognized by IgM antibodies also increased with the severity of disease (7.5±2.1 in stage III/IV versus 3±0.5 in stage 1/11 disease