Improved fusion technique. III. The growth promoting activity of lipopolysaccharide, dextran sulfate, and red cell lysate added to Hy-clone calf serum.

A new high quality young-calf serum, Hy-clone calf serum (HcCS), was tested for use in hybridoma culture. This calf serum alone had little growth promoting activity and was much inferior to fetal calf serum (FCS). Red cell lysate (RCL) used in combination with the young-calf serum showed very good growth promoting activity. Growth was increased about threefold over that in the presence of FCS. However, HcCS and RCL could not substitute for feeder cells when hybridomas were cultured as single cells under conditions of limiting dilution. It is thought likely that the potent growth promoting factor in red cell lysate is hemoglobin.