Identification of two granulocyte/macrophage colony-stimulating factors from porcine leukocyte cultures.

Granulocyte/macrophage colony-stimulating factors (CSF) were found in large-scale serum-free cultures of porcine blood leukocytes. The factors were concentrated from the conditioned culture medium of Concanavalin A-stimulated leukocytes using ammonium sulfate salting-out fractionation. The protein precipitate at 45-90% salt saturation contained two CSF types upon gel filtration on Sephadex G-100: One type was found to be active on mouse, but not on human bone marrow stem cells and had an apparent molecular mass of 85 000-100 000 Da; the other of about 40 000-45 000 Da stimulated both mouse and human bone marrow stem cells.