Effect of purified somatomedins on thymidine incorporation into lectin-activated human lymphocytes.

These data describe the effects of purified preparations of several growth factors on thymidine incorporation into phyto-haemagglutinin-activated (PHA) human lymphocytes. The somatomedins selected for this study included human somatomedins A and C, insulin-like growth factors (IFG1 and IGF2) and multiplication stimulating activity (MSA). Assays were carried out with and without serum. Complementary assays were performed with a low-molecular serum ultrafiltrate added to somatomedin C and to MSA. We found that all the peptides tested, except MSA, stimulated thymidine incorporation into PHA-activated lymphocytes in a dose-dependent manner, even though different doses were required to obtain a response. The data reported point out the multiplicity and the interrelationships of the serum factors involved in the stimulation of human cells growth.