Colony stimulating factor (CSF) in human mixed lymphocyte cultures: effect on human and mouse progenitor cells.

Supernatants from human two-way MLC, poor and rich in monocytes, were tested for their ability to induce colony growth of human and mouse progenitor cells in semi solid agar. Colony stimulating factor (CSF), with activity in both systems, indicated that allogenic lymphocytes require monocytes to produce CSF. Whereas human marrow showed an early kinetics of production, the liberation of CSF active on mouse marrow cells exhibited a delayed kinetics. These results, combined with other evidence, suggest that human lymphocytes produce two different factors.