The purification and quantitation of helper T cell-replacing factors secreted by murine spleen cells activated by concanavalin A.

A microculture assay with low numbers of athymic (nude) spleen cells has been used to quantitate the helper T cell-replacing activity secreted by concanavalin A-treated spleen cells. This quantitation allows an estimate of the recovery of biologic activity during concentration from culture supernatants by salt precipitation, and purification by gel filtration, ion exchange chromatography, and isoelectric focusing. The T cell-replacing activity is found in protein of 30 to 40,000 daltons size as estimated by gel filtration, but shows heterogeneity in electric charge. The activity is active at concentrations of less than 10(-9) M, and is strictly antigen dependent in its mode of action.