HORMONAL-REGULATION OF COMPLEMENT COMPONENTS AND RECEPTORS THROUGHOUTTHE MENSTRUAL-CYCLE

OBJECTIVES: Complement components have been recently demonstrated to b e present in the reproductive tract. Among these components, C3 synthe sis by glandular epithelium of the rat uterus has been shown to be reg ulated by estrogen; progesterone inhibits this synthesis. However, the hormonal regulation of C3 and the presence of other complement factor s in the human has not been investigated to date. In this study we exa mined the presence and the hormonal regulation of different complement components and receptors in the human endometrium at various phases o f the menstrual cycle of normally cycling women with no pelvic patholo gic abnormalities. STUDY DESIGN: Endometrial tissue was obtained from normally cycling women, and immunohistochemistry was performed by mean s of monoclonal antibodies against C3, factors B-1, decay-accelerating factor, membrane cofactor protein, and complement receptor types 1, 2 , and 3. The tissue was incubated with minimal essential media without methionine containing methionine labeled with sulfur 35. Immunoprecip itations were performed on the media with goat antihuman C3 antibody, and the proteins were analyzed by sodium dodecyl sulfate polyacrylamid e gel electrophoresis. RESULTS: C3 was found to be present in the glan dular epithelial cells of luteal endometrium. Biosynthesis as analyzed by immunoprecipitation with anti-C3 antibody was found to increase du ring the luteal phase of the cycle and to be minimal in the proliferat ive phase. Like C3, factor B and decay-accelerating factor were locali zed to the luteal glandular epithelial cells. In contrast, membrane co factor protein was found to be present in the glandular epithelium thr oughout the menstrual cycle, and complement receptor type 1 was presen t only in the stromal compartment of luteal endometrium. Complement re ceptor type 3 was present only in the infiltrating leukocytes in the l uteal endometrium, whereas complement receptor type 2 was undetectable . CONCLUSIONS: These findings suggest that several components of the c omplement system exist in the human endometrium in a hormone-dependent manner and may play a role in normal reproductive function.