Description: Human IL-7, also called lymphopoietin 1 (LP-1), a pre-B cell growth factor, is a ~28 kDa factor produced by bone marrow and thymic stromal cell and spleen cells. IL-7 is a stromal cell-derived growth factor for progenitor B cells and T cells. The main population in the thymus responsive to IL-7 is CD4-CD8-. It also stimulates proliferation and differentiation of mature T cells and NK cells.