Different optimal PHA concentrations for stimulation of Chinese hamster lymphocytes in cultures supplemented with foetal calf serum or horse serum.

Chinese hamster lymphocyte cultures were supplemented with foetal calf serum (FCS) or hose serum (HS). Addition of 2-mercaptoethanol (2-ME) to cultures supplemented with these sera resulted in a marked increase lymphocyte proliferation. The PHA concentrations necessary for optimal lymphocyte stimulation were much lower in cultures supplemented with HS than with FCS. Phytohaemagglutinin (PHA) concentrations optimal for stimulation of a given number of lymphocytes in cultures supplemented with FCS often gave inhibition of similar cultures supplemented with HS.