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Characterization of a Factor Required for the Differentiation of Myeloid and Lymphoid Cells in Vitro¹

From The Salk Institute for Biological Studies P. O. Box 1809 San Diego, California 92112

Abstract

The properties of a factor which is secreted by a cloned tumor cell line (JLS-V5) have been examined. The factor has been assayed in two culture systems. The factor induced the formation of colonies containing granulocytes and macrophages from mouse bone marrow cells cultured in a semi-solid agar medium. The factor also stimulated a normal primary immune response against erythrocyte antigens in immunologically unresponsive mouse spleen cultures. These spleen cultures were prepared from unimmunized mice in medium containing a deficient fetal bovine serum. The factor has been purified 500-fold from the serum-free culture supernatants of JLS-V5 cells. When the factor was treated with a variety of chemical and enzymatic reagents and then fractionated by gel filtration, the biologic activity for each culture assay resulted from the same molecular weight fractions. Acrylamide gel electrophoresis indicates the factor has a m.w. of 70,000 to 80,000.

Footnotes

¹ This work was supported by Ford Foundation Grant No. 7505, National Institute of Allergy and Infectious Diseases Research Grant No. AI05875, and National Institute of Allergy and Infectious Diseases Training Grant No. AI00430 to Dr. Melvin Cohn.