Stimulation of [3H]thymidine uptake in mouse marrow by granulocyte-macrophage colony stimulating factor from mouse lung conditioned medium.

Stimulation of [3H]thymidine uptake in mouse marrow cells by a haematopoietic factor, granulocyte-macrophage colony stimulating factor from mouse lung conditioned medium, was used to follow the activity of the factor in the medium, and during its partial purification from the medium. The assay was performed in microtitre plates and found to be much easier and faster than conventional colony counting. The marrow cells were incubated in flat-bottomed plates in the presence of the factor for 5 days before labelling with [3H]thymidine (2 muCi/well, 5 Ci/mmole) for 6 h. Stimulation of the [3H]thymidine uptake was compared with the development of granulocyte-macrophage colonies in semisolid methylcellulose culture. The activity followed by both assays showed identical behaviour when subjected to ammonium sulphate precipitation, Sephadex gel filtration, concanavalin-A-Sepharose chromatography and polyacrylamide gel electrophoresis.