Stimulation and inhibition of mitogen-induced lymphoproliferation by serum fractions

Normal guinea pig serum was fractionated by filtration through a Sephacryl S200 column. The various fractions were assayed on concanavalin A and phytohemagglutinin-induced mitogenesis as measured by 3H-thymidine uptake in newly formed DNA. Alpha-Globulin, gamma-globulins and albumin were shown to modulate lymphoproliferation. The enhancing or depressing effects of these various fractions depended upon the nature and dose of the mitogen used, the concentration of the fraction added, and the time interval between the addition of fractions and the addition of mitogens. The results suggest that serum fractions can at least modulate the immune response through their activity on the proliferation of lympohocytes.