This is a model of human Interleukin-2 (IL-2). IL-2 is a cytokine signaling molecule that plays an active role in our immune system. This protein helps regulate white blood cells and is also part of the body's natural response to microbial infection. During an immune response, antigen binding to the T cell receptor (TCR) stimulates expression of IL-2 and the IL-2 receptor. IL-2 binding to it's receptor stimulates the growth, differentiation and survival of antigen-specific CD4+ T cells and CD8+ T cells, contributing to immunological memory. In addition, IL-2 is required during T-cell development in the thymus, and is necessary in T-cell recognition between self and non-self.