Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) was initially characterized as a growth factorthat can support the in vitro colony formation of granulocyte-macrophage progenitors. It is produced by anumber of different cell types (including activated T cells, B cells, macrophages, mast cells, endothelial cellsand fibroblasts) in response to cytokine of immune and inflammatory stimuli. Besides granulocyte-macrophageprogenitors, GM-CSF is also a growth factor for erythroid, megakaryocyte and eosinophil progenitors. Onmature hematopoietic, monocytes/ macrophages and eosinophils. GM-CSF has a functional role on nonhematopoitic cells. It can induce human endothelial cells to migrate and proliferate. Additionally, GM-CSF canalso stimulate the proliferation of a number of tumor cell lines, including osteogenic sarcoma, carcinoma andadenocarcinoma cell lines.