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Fractionation of Spleen and Serum in Attempts to Isolate the Radiation-Leukemia Protection Factor¹

Cancer Research and the Departments of Medicine, Biochemistry, Pathology, Psychiatry, and Medical Genetics, Indiana University Medical Center, Indianapolis, Indiana 46202

The leukemia induced in C57BL mice by X-irradiation can be prevented by injection of extracts of sheep spleen or serum. These materials have been fractionated by ammonium sulfate precipitation followed by chromatography on Sephadex G-200. Radiation-leukemia protection (RLP) activity precipitates partially between 0–40% and 40–60% saturation with ammonium sulfate. During chromatography on Sephadex, most of the leukemia protective activity appears to elute with the higher molecular weight proteins of sheep spleen but with the smaller proteins of sheep serum. Cohn fractions III, III-0, IV-1, and IV-4 from commercial sources have shown RLP activity on one or more tests. All the preparations tested were heterogeneous on polyacrylamide gel electropherograms. It is suggested that more than one polypeptide exhibits leukemia protection activity.

¹ Supported in part by a contract with the United States Atomic Energy Commission, AT(11-1) 1391 and the Indiana Elks. Taken in part from a thesis submitted by Don B. Clewell to the Graduate School, Indiana University, in partial fulfillment of the requirements for the Ph.D. degree.

² Supported by a training grant (TI CA 5066) from the National Cancer Institute. Present address: Department of Biology, University of California, San Diego, La Jolla, California.

Received 4/10/67. Accepted 2/11/69.