Interleukin 7 (IL-7) is a hematopoietic cytokine that is constitutively produced by stromal cells from the bone marrow and thymus. IL-7 signals through the IL-7R to promote the differentiation of hematopoietic stem cells to lymphoid precursor cells, which give rise to T cells, B cells, and natural killer cells. and IL-7 show species cross-reactivity. Recombinant IL-7 is a non-glycosylated Protein, containing 153 amino acids, with a molecular weight of 17.4 kDa.