Chromatographic separation of a rat serum growth factor required by Trypanosoma lewisi

Rat serum globulins promote the growth of T. lewisi in the mouse, which is usually refractory to this parasite (Greenblatt and Lincicome, 1966). DEAE (diethylaminoethyl) cellulose column chromatography utilizing the solvent described by Levy and Sober (1960) allows separation of the 7S γ₂ globulin from those proteins which have the electrophoretic mobility of the β globulins. The parasitemia-promoting activity lies in the latter group of proteins. These fractions from the DEAE columns contained proteins that clustered into three classes with sedimentation coefficients of ∼ 4S, ∼7S, and ∼ 19S. Their resolution was accomplished on Sephadex G-200 columns and activity resided in the 7S fraction. This material was homogeneous by the criteria of ultracentrifugation, acrylamide gel disc and paper electrophoresis, but had considerable complexity on immunoelectrophoresis. A DEAE-Sephadex column produced simplification of the patterns so that active material was found to be confined to three very closely placed precipitin lines. A beginning has been made in quantitating the degree of purification of the active material. The nature of the material is discussed, as well as its relation to other growth stimulating and inhibiting factors.