Partial Purification and Characterization of an Antigen-specific Helper Factor Synthesized by a T-cell Continuous Line

Antigen-specific factors produced by the T-cell growth factor-dependent T-cell continuous line E-9M(+) were partially purified. Gel analysis of the twice-affinity-purified eluate of a poly(Tyr,Glu)-poly(DLAla)--poly(LLys) [(T,G)-A--L] column revealed the existence of iodinated bands with molecular weights of 17,000 and 15,000, in addition to a diffuse band of high molecular weight. The specific helper activity of the E-9M(+) supernatants was associated with a precipitate from 65-75% ammonium sulfate. Gel electrophoresis of either the eluate of a (T,G)-A--L column or of the 65-75% salt precipitate indicated that in both preparations two fractions contained the biological activity of the factor, one of a high (less than 67,000) molecular weight and the other of a low (15,000-17,000) one. Culture supernatants of the internally [35S]methionine-labeled E-9M(+) line were subjected to a combined purification of sequential ammonium sulfate precipitations, followed by affinity chromatography. Polyacrylamide gel patterns obtained of the eluates of the different salt precipitates demonstrated that the 65-75% ammonium sulfate precipitate contained two 35S-labeled bands with apparent molecular weights in the range of 60,000 and 15,000, similar to the activity patterns obtained by the gel electrophoresis fractionation experiments. Thus, it is suggested that a fraction of low molecular weight preserves the antigen specificity and the helper activity of the factor produced by the T-cell line.