Human Interleukin-4 (IL-4) is a cytokine that plays an important role in regulating inflammation and immune responses. It induces the differentiation of T cells to Th2 cells. This cytokine binds the IL-4 receptor that also binds another cytokine interleukin 13 (IL-13), which may explain the overlapping functions of IL-4 and IL-13. IL-4, originally designated as B-cell growth factor-1 (BSFl), is described in the supernatant of activated EL-4 thymoma cells as a factor that can co-stimulate B-cells activated with submitogenic concentrations of anti-IgM.
