The MP4-25D2 monoclonal antibody specifically binds to Interleukin-4 (IL-4). IL-4 is also known as Lymphocyte stimulatory factor 1, B cell stimulatory factor 1 (BSF-1), or B cell growth factor 1 (BCGF-1). IL-4 is produced by activated T cells, basophils, and mast cells. IL-4 is a multifunctional cytokine and growth factor that affects a variety of different target cell types. IL-4 can costimulate T cell proliferation and survival, as well as help drive Th2-like cell differentiation and effector functions. It costimulates B cell proliferation and survival, and can help B cells differentiate into IgG4- or IgE-producing cells. IL-4 can also diminish the proinflammatory functions of monocytes and macrophages. IL-4 exerts its biological effects by binding with high affinity to cell surface CD124 (IL-4Rα chain). CD124 forms signaling IL-4 receptor complexes with either CD132/common γ chain or CD213a1/IL-13Rα1 to form either Type I or Type II IL-4 Receptor complexes, respectively. The immunogen used to generate the MP4-25D2 hybridoma was purified recombinant human IL-4. This is a neutralizing antibody. The MP4-25D2 antibody has been reported to crossreact with IL-4 from rhesus monkeys. The use of the MP4-25D2 antibody for epitope mapping of human IL-4 has been described.