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IL-7 is a hematopoietic growth factor secreted by stromal cells in the bone marrow and thymus. It is also produced by keratinocytes, dendritic cells, hepatocytes, neurons, and epithelial cells, but is not produced by normal lymphocytes. IL-7 stimulates the differentiation of multipotent （pluripotent） hematopoietic stem cells into lymphoid progenitor cells. It also stimulates proliferation of all cells in the lymphoid lineage （B cells, T cells and NK cells）. It is important for proliferation during certain stages of B-cell maturation, T and NK cell survival, development and homeostasis. This cytokine can be produced locally by intestinal epithelial and epithelial goblet cells, and may serve as a regulatory factor for intestinal mucosal lymphocytes. IL-7 could also be beneficial in improving immune recovery after allogenic stem cell transplant.