The MP2-8F8 monoclonal antibody reacts with mouse IL-3, a pleiotropic cytokine produced primarily by activated T cells but also by activated mast cells, keratinocytes and neurons/astrocytes. IL-3 is highly species-specific, mature human and mouse IL-3 share only 29% sequence identity and human IL-3 does not show activity on mouse cells. IL-3 can stimulate the proliferation and differentiation of megakaryocytes, neutrophils, and macrophages from bone marrow cultures. Additionally, IL-3 also affects the functional activity of mature mast cells, basophils, eosinophils and macrophages. The MP2-8F8 antibody has been reported to neutralize the bioactivity of natural or recombinant IL-3 as well as stimulate basophil proliferation when administered as a complex with IL-3.