Interleukin-4 (IL-4) is a pleiotropic cytokine that has many roles, such as inducing the differentiation of naïve helper T cells (Th0 cells) to Th2 cells, stimulating activated B-cell and T-cell proliferation, and promoting immunoglobulin class switching to IgG1 and IgE in mouse B-cells. IL-4 is expressed by CD4 T-cells, mast cells, basophils and eosinophils. IL-4 was previously known as B-Cell Differentiation Factor (BCDF) or B-cell Stimulatory Factor (BSF1). The 11B11 monoclonal antibody specifically binds to mouse IL-4. The immunogen used to generate the 11B11 hybridoma was partially purified mouse IL-4 prepared from the supernatant of Phorbol 12-Myristate 13-Acetate (PMA)-stimulated EL-4 cells. The 11B11 antibody is reportedly a neutralizing antibody.