Macrophage colony-stimulating factor is produced by human T lymphoblastoid cell line, CEM-ON: identification by amino-terminal amino acid sequence analysis.

A subclone, designated CEM-ON, derived from an azaguanine-resistant human leukemic T cell line, CEM-AG(R), constitutively secretes a colony-stimulating factor (CSF) which stimulates the production of macrophages from murine bone marrow progenitor cells. This CSF has been purified from serum-free conditioned medium. Highly purified CEM-ON CSF with a specific activity of 4.7 X 10(7) units/mg protein was obtained. Amino-terminal sequence analysis showed that the first 27 amino acids were identical to the amino-terminal sequence of the M-CSF (CSF-1) based on the cDNAs for human M-CSF. On SDS-PAGE analysis, CEM-ON CSF had an apparent molecular weight of 33,000-43,000; following reduction with 2-mercaptoethanol, this migrated as a 20,000-24,000 subunit, suggesting a homodimer structure. These results show that a human T cell line, CEM-ON, secretes M-CSF into its medium.