Purification of an immunosuppressive principle from Ehrlich carcinoma ascites

An immunosuppressive factor was purified from Ehrlich carcinoma ascites by the combination of ultrafiltration and Sephadex chromatography. The resulting product showed 50% reduction in the number of splenic plaque-forming cells in mice immunized with sheep red blood cells when as low as 50 mug dose was given twice intraperitoneally before erythrocyte injection. The molecular size of the product was between 30,000 and 100,000, and it was relatively heat unstable.