Macrophage colony-stimulating activity is produced by three different EBV-transformed lymphoblastoid cell lines.
The lymphoblastoid cell lines BLY 9.84, Gl, and Pl constitutively release a colony-stimulating activity (CSA) which specifically stimulates murine macrophage progenitor cells in vitro. The biochemical characterization of BLY 9.84-derived CSA exhibits a molecular size of apparently 150-200 kDa even under dissociating conditions with 6 M guanidine hydrochloride or inhibition of glycosylation. Production of this CSA is inhibited by cycloheximide and its activity is destroyed by reduction with dithiothreitol. Replating experiments give evidence for a functional similarity with CSF-1 (macrophage colony-stimulating factor).