PRODUCTION BY MOUSE SPLEEN-CELLS OF FACTORS STIMULATING DIFFERENTIATION OF MOUSE MYELOID LEUKEMIC-CELLS THAT DIFFER FROM THE COLONY-STIMULATING FACTOR

Abstract

Mouse myeloid leukemic M1 cells can be induced to differentiate into macrophages and granulocytes in vitro by a protein inducer, differentiation-stimulating factor (D-factor) and by various other compounds. Mouse spleen cells produced D-factors when treated with various mitogens, such as concanavalin [Con] A, phytohemagglutinin [PHA], pokeweed mitogen [PM], lipopolysaccharide [LPS] and synthetic double-stranded polyribonucleotide copolymer of polyinosinic and polycytidylic acids. Con A, PHA and PM stimulated spleen lymphocytes, but not spleen macrophages, to produce a D-factor with an apparent MW of 40,000-50,000. LPS and copolymer of polyinosinic and polycytidylic acids stimulated spleen lymphocytes and spleen macrophages to produce D-factors. Spleen macrophages produced D-factors with MW of 40,000-50,000 and 20,000-25,000; spleen lymphocytes produced only the larger molecules. Colony-stimulating factor (CSF) and interferon were also detected in conditioned medium of spleen cells treated with Con A or LPS. On gel filtration of the conditioned medium with sephadex G-100, CSF was eluted between the larger D-factor and the smaller one. The fraction with interferon activity overlapped that of the larger D-factor. Incubation of the conditioned medium at pH 2 abolished the activity of interferon but did not affect the activity of D-factor or CSF. The addition of cytochalasin B suppressed the production of interferon but not of D-factor or CSF by the spleen cells. The D-factor is a different substance from CSF or type II interferon.