[C3 stimulates the proliferation of human pre-B Raji cells]

In a defined medium in which transferrin (3 micrograms/ml) was the only source of exogenous proteins, Raji cells of the human pre-B lymphoblastoid cell line died within 48 h after forming polykaryons. The simple addition of purified C3 at a concentration equal to or higher than 3 micrograms/ml allowed Raji cells to divide. This preliminary report provides a defined system for studying the mitogenic effect of human C3 or C3 fragments upon proliferation of human B-cells lines.