Bovine lung conditioned medium as a source of both human and murine colony-stimulating factor

Medium conditioned by bovine lung tissue (BLCM) contains a factor (CSFBL) that can stimulate either murine or human bone marrow cells to form colonies. CSFBL was partially purified by gel filtration and DEAE-cellulose chromatography. The specific activity was determined using both target systems. In all stages of purification the specific activity on human bone marrow was about 2 times greater than on mouse bone marrow. Determination of the molecular weight of CSFBL by gel filtration and comparison with mouse lung CSF (CSFML) revealed that both are similar in size, having an apparent molecular weight of 29,000 d. CSFBL stimulates only granulocyte colonies, neither macrophage nor mixed colonies could be detected in either bone marrow assay. These results and the ease of preparation recommend BLCM as a suitable starting for large scale preparation of CSF active on human cells.