IL-2 signals through the IL-2R receptor in order to induce the proliferation of activated T cells. IL-2 also stimulates proliferation and differentiation of B cells, natural killer cells, monocytes and macrophages. Recombinant human IL-2 produced in E. coli is a non-glycosylated protein, made up of 134 amino acids with a molecular mass of 15.5 kDa. rHu IL-2 has a Ser substitute for Cysteine at position 126.