Conditioned medium prepared from human autopsy lung tissue contains high level activity of colony stimulating factor which stimulates granulocytes and macrophage colony formation in both mouse and human bone marrow. The lung colony stimulating factor has been purified about 2250-fold by methods including hydroxylapatite chromatography, preparative gel electrophoresis, preparative isoelectric focusing, and gel filtration chromatography. The final specific activity was 2.7 X 106 units/mg. The purified factor has a molecular weight of 41 000 as determined by gel filtration. It is stable at the pH range of 6.5-10 and at 56 °C for 30 min but sensitive to protease digestion and periodate oxidation. On polyacrylamide gel electrophoresis, it migrates in the ±-globulin post-albumin region. Upon isoelectrofocusing lung colony stimulating factor appears heterogeneous with isoelectric points of 3.7-4.3. Treatment with neuraminidase did not affect its activity, but caused a change in electrophoretic mobility and isoelectric point. Antibody produced by immunizing rabbits with partially purified lung colony stimulating factor exerted strong inhibitory activity on the factor from lung as well as on colony stimulating factor from other human sources including serum, urine, and placenta.
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