IL-4 (interleukin 4) is a pleiotropic cytokine. It regulates diverse T and B cell responses including cell proliferation, survival and gene expression. IL-4 regulates the differentiation of naive CD4+ T cells into helper Th2 (T helper) cells, characterized by their cytokine-secretion profile th at includes secretion of IL-4, IL-5, IL-6, IL-10, and IL-13, which favor a humoral immune response. Another dominant function of IL-4 is the regulation of immunoglobulin class switching to the IgG1 (immunoglobulin G1) and IgE isotypes. Excessive IL-4 production by Th2 cells has been associated with elevated IgE production and allergy. IL-4 helps in long-term recovery after cerebral ischemia by controlling the activities of microglia/macrophage. In mice, absence of IL-4 is associated with a state anxiety-like behavior.
