IMMUNOBLOT DETECTION OF DECREASED ANTIBODIES TO HAPTOGLOBIN-LIKE PROTEIN IN THE SERUM OF INFERTILE WOMEN WITH OR WITHOUT ENDOMETRIOSIS

The purpose of this study was to find out differences in the levels of antibodies to distinct antigens in the serum of fertile versus infert ile patients with and without endometriosis and to identify these anti gens. Blood was collected from 61 patients undergoing laparoscopy for pelvic pain, infertility, or tubal ligation. Serum antibodies against serum antigens with apparent molecular masses of 22 kDa and 18 kDa wer e assessed by immunoblot analysis. Gel filtration, HPLC DEAE ion-excha nge chromatography, NH2-terminal sequencing, and double immunodiffusio n were used to characterize and identify these proteins. The relative amount of antibodies reacting with 22- and 18-kDa proteins detected in a standard preparation of antigens was significantly lower in the ser um of infertile patients with endometriosis (0.20 +/- 0.05 and 0.57 +/ - 0.10) and without endometriosis (0.21 +/- 0.06 and 0.53 +/- 0.08) co mpared to that of control fertile women without endometriosis (0.53 +/ - 0.08 and 1.09 +/- 0.13). After purification by chromatography, the N H,terminal amino acid sequence of the proteins in the 22- and 18-kDa r ange was identical through 20 amino acids with the alpha chain of the human haptoglobin. Double immunodiffusion implied immunochemical ident ity between commercial human haptoglobin and the purified proteins. We conclude that infertile patients with and without endometriosis show reduced serum levels of antibodies against a haptoglobin-like protein. These results would indicate an alteration of the immune system or ch anges in the levels of these antigens in infertility and/or endometrio sis.