A granulocyte colony-stimulating factor from serum-free cultures of RSP-2 X P 3 cells: its separation from a macrophage colony-stimulating factor and its biological and molecular characterization.

A granulocyte colony-stimulating factor (G-CSF) was highly purified from the serum-free culture medium of RSP -2 X P3 cells. The G-CSF had an apparent molecular weight of 33,000 as determined by high speed gel permeation chromatography, but its molecular weight was decreased to 15,000 by 0.1% sodium dodecyl sulfate. A small amount of monocyte/macrophage CSF (M-CSF) also was separated from the same medium. The production of this M-CSF was increased markedly by bacterial lipopolysaccharides. The M-CSF had an apparent molecular weight of 77,000 in the absence of 0.1% SDS and 49,000 in its presence. The G-CSF was stable against 5 mM dithiothreitol, whereas the M-CSF was slowly inactivated. The two CSFs also differed in their heat-stability and resistance to trypsin. Neuraminidase changed the isoelectric point of both CSFs. Anti-L cell CSF serum severely inhibited the activity of M-CSF but not that of G-CSF. A 1 : 1 mixture of M-CSF and G-CSF developed colonies of the respective types, both in excess of the number predicted. The RSP -2 X P3 G-CSF reported here should prove very useful in the study of differentiation in myeloid stem cells.