No direct activation of fluid phase C3 by lymphokines

Supernatants of stimulated (PPD or Con A) or unstimulated guinea pig lymph node cell cultures in serum-free medium were fractionated on Sephadex G 75. The fractions were tested for C3-consuming activities in a hemolytical assay. No C3 consumption could be detected in any fraction (MW range 80,000 to 10,000). The same result was obtained by extending the fractionation range using Sephadex G 200. A lytic activity with a molecular weight of appr. 225,000 which lysed EAC 14 cells in the presence of C2, 5, 6, 7, 8, 9 was attributed to serum C3 contaminating the cultures. It was determined that C3 is not produced in significant amounts by lymphocyte cultures.