ABSTRACT
BACKGROUND: The membrane-associated proteins that regulate human complement activation are ubiquitously expressed and function cooperatively to protect cells from autologous complement damage. For classical and alternative pathways, the primary regulators at the stage of C3 proteolysis and deposition are membrane cofactor protein (MCP; CD46) and decay-accelerating factor (DAF;CD55), whereas protectin or CD59 regulates terminal component assembly. There is increasing awareness in reproductive, tumor, and transplantation immunology of the conventional and non-complement roles of these proteins. The human reproductive system may serve as a model of the non-complement functions. METHODS: We performed immunohistochemical analyses of multiple normal ovaries, fallopian tubes, cervices, and uterine corpi by using well-characterized monoclonal antibodies to provide a detailed, direct comparison of complement regulator expression. RESULTS: Membrane cofactor protein was diffusely and strongly expressed on all epithelia and vascular endothelium and was the predominant regulator on oocytes. In contrast, decay-accelerating factor had variable expression in intensity and distribution on epithelia and was notably absent on certain epithelia and oocytes. It was the only regulator present on the connective tissue between muscle bundles in the myometrium and the cervix and was found on most stroma. CD59, although staining intensity varied, was present on virtually all epithelia, vascular tissue, and stroma. CONCLUSIONS: Distinct reproducible patterns of complement regulator expression are found throughout the female reproductive tract. Differential expression on certain epithelia and oocytes may suggest non-complement activities. This comprehensive study should provide a basis for further characterization of pathological tissues and mechanisms of cellular localization.
