Human IL-2 Recombinant Protein. Interleukin 2 (IL-2) is an immuno-modulatory cytokine that is important for the proliferation of activated T cells, differentiation of B cells, natural killer cells, monocytes and macrophages. IL-2 signals through the IL-2 receptor (IL-2R), a heterotrimeric protein complex whose gamma chain is also shared by interleukin 4 (IL-4) and interleukin 7 (IL-7). The expression of the IL-2 gene in mature thymocytes is monoallelic, which represents an unusual regulatory mode for controlling the precise expression of a single gene. The targeted disruption of a gene similar to IL-2 in mice leads to an ulcerative colitis-like disease that suggests an essential role of this gene in the immune response to antigenic stimuli.