Interleukin-4 (IL-4) is a Th2 cytokine produced primarily by activated Th2 cells, but also by basophils, mast cells, and nuocytes. IL-4 increases proliferation of B-cells in response to LPS or anti-IgM, and increases the expression of class II MHC antigens, the IgE receptor, and the IL-4 receptor on B-cells. IL-4 inhibits NK cell activation and proliferation as well as IL-2-induced LAK activation. IL-4 induces the differentiation of "alternatively activated" macrophages (M2 macrophages). Cayman's IL-4 (mouse) EIA Kit is an immunometric (i.e., sandwich) EIA that permits IL-4 measurements within the range of 0-100 pg/ml, with a limit of detection of 3.1 pg/ml.