Synthesis of the second and fourth components of complement by tissue culture cell lines

A number of tissue culture cell lines were tested for synthesis of C1, C2 and C4. Supernates from two human embryo cell lines were positive for C1 when received, but on further culturing gave only slight amounts of C1. A number of cell lines produced C2 over a long period. This production was followed in hybrid cells formed by cell fusion. Some mixed rat liver cell cultures produced both C2 and C4. Of 30 tissue cultures tested, seven were found to synthesize C2. A cell line derived from guinea pig peritoneal cells produced C2 when grown with heat‐inactivated serum or in a synthetic medium. About 310 effective C2 molecules were produced per hour per cell. Unlike fresh peritoneal cells, production of C2 by the cell line was unaffected by hydrocortisone. Addition of stimulated or unstimulated lymphocytes with or without macrophages did not alter C2 production.