Endometrial synthesis and secretion of complement component-3 by patients with and without endometriosis

In the present study we examined complement-3 (C3) synthesis and secretion from early proliferative endometrium of infertile patients with and without endometriosis. One gram of tissue was obtained by endometrial sampling at the time of diagnostic laparoscopy and incubated for 12 to 16 hours in the presence of radioactive methionine. Immunoprecipitation was performed with rabbit antihuman C3 immunoglobulin G and only a single 180-kDa radiolabeled protein (C3) was immunoprecipitated. This protein dissociates into 113- and 69-kDa subunits in the presence of dithiothreitol. The amount of C3 produced and secreted by the endometrium was quantitated as a percentage of counts per minute recovered by immunoprecipitation. Patients with minimal endometriosis produced significantly greater amounts of endometrial C3 than patients with no endometriosis or patients with severe endometriosis.