Abstract
Evidence is provided which demonstrates that conditioned media of cultured endothelial cells derived from human umbilical veins contained a factor which stimulated peripheral blood mononuclear cell [
3H]thymidine uptake. A dose-dependent response in peripheral blood mononuclear cell [
3H]thymidine uptake was obtained when cells were incubated with increasing concentrations of supernatant of endothelial cell cultures. Studies on temporal kinetics demonstrated that stimulatory activity was evident when mononuclear cells had been incubated with endothelial cell supernatant for 120 hr or more. Preliminary characterization showed the growth immunoregulatory factor to have a molecular weight > 100,000 Da.