Adherent Cell Dependent Colony‐Stimulating Activity in Human Serum: A Granulopoietic Regulator?

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Abstract
Bacterial infections and trauma which increase production of granulocytes and monocytes by the bone marrow may do so through factors in serum capable of stimulating growth of granulocyte-macrophage cells in vitro. Human serum possesses 2 types of colony stimulating activity (CSA), one which stimulates granulopoietic progenitor cells directly and another which results from the interaction of serum and bone marrow adherent cells (monocyte-macrophages) or peripheral blood leukocytes: adherent cell dependent CSA. These activities were due to different factors which may be separated by gel filtration. Sera of 7 patients undergoing hysterectomy who developed post-operative infection showed post-operative elevation of the adherent cell dependent activity in all cases but no change in direct acting CSA. The direct acting CSA in human serum apparently does not represent the principal humoral message to the bone marrow from sites of trauma and infection in the tissues; granulopoiesis may be controlled indirectly by the action of a different humoral factor which increases production of CSA by marrow monocyte-macrophages. Preliminary experiments suggest that lymphocytes stimulated by bacterial products may be 1 source of this factor.