BIOSYNTHESIS AND SECRETION OF THE 3RD COMPONENT OF COMPLEMENT BY HUMAN-ENDOTHELIAL CELLS-INVITRO

Abstract

The third component of complement (C3) is synthesized and released by cultured human capillary endothelial cells. After the incubation of cells in a methionine-free medium containing 35S-methionine for 48 hr, culture supernatants were immunoprecipited with anti-human C3 serum. SDS solubilization and 2-ME reduction of the immunoprecipitates, followed by separation with SDS-polyacrylamide gel electrophoresis and autoradiography, revealed two major bands comparable to those of the .alpha. and .beta. chains of human C3. The content of C3 in the culture medium harvested at different time-intervals was determined by ELISA. The C3 secretion rate was about 250 ng/106 cells/5 days in the primary culture medium and 75 ng/106 cells/5 days after seven passages. The capillary endothelial cells described here have factor VIIRAg specific for endothelial cells, and exhibit ring formation resembling capillary lumina, but they lack Weibel-Palade bodies.