Interleukin-3 is primarily secreted by T-lymphocytes and mast cells. In vitro studies have shown that IL-3 supports the growth of very early hematopoietic pro-genitor cells and acts synergistically with other CSFs, such as EPO, GM-CSF, and G-CSF in the process of ery-throid, myeloid, and megakaryocyte cell proliferation. Interleukin-3 has been shown to induce proliferation of blood lymphocytes and to potentiate the proliferation