SYNTHESIS OF COMPLEMENT PROTEINS IN AMNION

The amnion is a metabolically active tissue that has been identified a s a site of synthesis of numerous products., We report that amnion tis sue explants and amnion-derived epithelial cells synthesize and secret e six proteins of the the complement system, Clr, Cls, Cl inhibitor, f actor B, C3, and factor H. Synthesis of C2 was minimal and variable, a nd C5 was not detected. The sis synthesized proteins had size and subu nit composition characteristic of proteins synthesized in HEp2, a long term cell line derived from malignant epithelial cells. Constitutive and regulated synthesis of five of the six proteins was similar in amn ion tissue and cells. However, synthesis of factor B was different in tissue and cells; constitutive synthesis was 12-fold higher in tissue than in cells, and interleukin-l did not alter synthesis in tissue, bu t increased synthesis by 11.7-fold in cells. These results indicate th at amnion may be a source of complement proteins present in the amnion fluid and may contribute to local host defense along with endometrial glandular epithelial cells, which synthesize C3. Furthermore, our res ults suggest that amnion tissue is stimulated in vivo to synthesize fa ctor B and cannot respond to interleukin-l with a further increase in the synthesis rate.