Partial purification and characterization of an endogenous granulomonopoiesis inhibitor from calf spleen

A factor which specifically inhibits the proliferation of murine bone-marrow-cell colonies in vitro was extracted from calf spleen and partially purified. No comparable inhibition in T-lymphocyte or erythrocyte assays was observed, suggesting a possible chalone nature of the factor. The formation of granulocyte and macrophage colonies is inhibited to equal degrees. The factor was found to be non-toxic: Bone-marrow cells exposed to the factor for 5 h proliferated at a normal rate thereafter. Solubility, molecular mass and ionic exchange data of the factor are similar to those found for chalone-like inhibitors derived from other sources. The present inhibitor however does not contain a thiol group, and has no stimulatory effect after oxidation as described previously for similar factors.