Supernatant Factors from Short-Term Cultures of Thymocytes: Effect on DNA Synthesis

Abstract

Supematants from cultures of unstimulated guinea pig thymocytes were investigated on allogenous thymocytes as regards conditioning effect. DNA synthesis was measured by incorporation of ³H-thymidine. Supematants taken after different incubation times up to 24 h were used. When used without concentration all supematants showed stimulating activity. After concentration and fractionation, a stimulating factor was found in supematants taken after a culture time of 24 h. This factor had a molecular weight above or equal to 70,000 daltons as indicated by gel chromatography. In the same supematants also an inhibiting factor was indicated.