IL-3 is a highly species-specific pleiotropic factor produced primarily by activated T cells though also by mast cells keratinocytes, and astrocytes, which stimulates colony formation of megakaryocytes, neutrophils, and macrophages from bone marrow cultures. The MP2-8F8 antibody reacts with mouse interleukin-3 (IL-3). The MP2-8F8 antibody can neutralize the bioactivity of natural or recombinant IL-3.