M-GM-CSF is produced in response to a number of inflammatory mediators by mesenchymal cells present in the hemopoietic environment and at peripheral sites of inflammation. GM-CSF is able to stimulate the production of neutrophilic granulocytes, macrophages, and mixed granulocyte-macrophage colonies from bone marrow cells and can stimulate the formation of eosinophil colonies from fetal liver progenitor cells. GM-CSF can also stimulate some functional activities in mature granulocytes and macrophages. GM-CSF receptors shows significant homologies with other receptors for hematopoietic growth factors, including IL2 -beta, IL-3, IL-6, IL-7, EPO and the Prolactin receptors. Recombinant mouse GM- CSF produced in E.Coli is a single, non-glycosylated, polypeptide chain containing 125 amino acids and having a molecular mass of 14,285.35 Daltons.