Interleukin-2 (IL-2, also known as T-cell growth factor, TCGF) is a lymphokine produced by lectin- or antigen-activated T-cells. It plays an important immunoregulatory role. This factor was first identified by its ability to promote the long-term in vitro proliferation of activated T-cells. It also promotes the generation and proliferation of cytotoxic T-cells, natural killer (NK) cells, and lymphokine-activated killer (LAK) cells. IL-2 also induces other lymphokines such as interferon-γ and B-cell growth factor (BCGF-1).