Mouse IL-2 is a 17kDa protein produced by activated CD4+ T helper cells immediately after foreign antigens bind with the T-cell receptor. IL-2 is an initiator of the acquired immunity and a major clone expansion stimulator of activated T cells. The cytokine stimulates the growth, proliferation and differentiation of native T-cells into “effecter T-cells”, promotes the survival of antigen specific “memory T-cell”, and stimulates the maturation of “regulatory T-cells”. The biological activity of IL-2 is mediated by receptor that is expressed primarily on the cell membrane of activated T-cells. IL-2 receptor is comprised of a specific alpha subunit with high affinity to IL-2, a beta subunit, and a common gamma subunit that is also involved with the biological functions of a number of other cytokines such as IL-4, IL-7, IL-9, IL-15 and IL-21.