Murine SF-20 is a bone marrow stroma-derived growth factor. SF-20 is expressed in bone marrow, spleen stroma cells, resting mononuclear cells, resting CD8+ and CD19+ cells, and activated CD8+ T cells, and has been shown to bind to the surface of cells expressing the receptor TSA-1 (Thymic shared Ag-1). Among its biological activities, SF-20 stimulates the proliferation of FDC-P2 cells (a mouse factor-dependent hemopoietic cell line) and mouse lymphoid cells. Recombinant Murine SF-20 is a 15.8 kDa protein containing 143 amino acid residues.