Interleukin 2 (IL-2) is a cytokine that produced predominantly by Th cells, stimulates the growth and differentiation of B cells, T cells, NK cells, and monocyte/macrophages. IL-2 signals through a receptor complex consisting of the IL-2Rα subunit, IL-2Rβ subunit, and γc, which activates the JAK/STAT pathway, especially STAT3 and 5, leading to gene transcription.