IL-7, Interleukin 7, is a protein that in humans is encoded by the IL-7 gene. IL-7 a hematopoietic growth factor secreted by stromal cells in the red marrow and thymus. It is also produced by keratinocytes, dendritic cells, hepatocytes, neurons, and epithelial cells but is not produced by lymphocytes. By the combination of approaches, IL-7 is located on 8q12-q13. IL-7 is critical for early T-cell development and homeostasis of naive and memory CD8-positive T cells. It signals through the IL-7 receptor complex, which consists of the IL7R-alpha chain and the common IL2R-gamma chain is critical for early T-cell development and homeostasis of naive and memory CD8 -positive T cells. It signals through the IL-7 receptor complex, which consists of the IL7R-alpha chain and the common IL2R-gamma chain.