Large-scale production of high-titered (10(2.2) to 10(4) U/ml) immune interferon (type II) was carried out in roller cultures of mouse spleen cells by using the T-cell mitogen staphylococcal enterotoxin A. Precipitation of 90% of this interferon by 55 to 80% saturated ammonium sulfate resulted in a 20-fold concentration and a two- to sixfold purification. After application of this interferon to either bovine serum albumin (BSA)-Affi-Gel 10 or hydroxylapatite columns, 100% of the interferon activity was recovered. By BSA-Affi-Gel 10 chromatography, 7% of the recovered activity was not bound, 45% was eluted with pH gradient 5 to 7, and 48% was eluted with 1 M NaCl. The pH- and salt-eluted interferons from the BSA-Affi-Gel 10 column were purified 62- and 390-fold, respectively, when compared with the starting materials. Rechromatography of the pH- and salt-eluted interferon peaks from the BSA-Affi-Gel 10 column did not alter their elution patterns. Stepwise elution of interferon from the BSA-Affi-Gel 10 columns with buffers of various pH and salt contents also resulted in greater than 300-fold purification. Specific activities of up to 2 x 10(5) U of interferon per mg of protein were attained with either elution procedure from BSA-Affi-Gel 10 columns. By hydroxylapatite chromatography, 5% of the recovered activity was not bound, 20% was eluted with a salt gradient, and 75% was eluted with 30% glycerin. Purification was 107- and 16-fold, respectively, for the two fractions. Ultrogel AcA 34 chromatography of the interferon resulted in two peaks of activity, a major one with a molecular weight of approximately 40,000 and a minor peak of molecular weight 70,000 to 90,000. Thus, by different types of chromatography, immune interferon was found to be heterogeneous.