APRIL, a member of the TNF superfamily, is expressed in monocytes, macrophages, certain transformed cell lines, certain cancers of the colon, and lymphoid tissues. APRIL, along with another TNF family member, BAFF, competes for two receptors, TACI and BCMA. APRIL has the ability to stimulate proliferation of various tumor cell lines, including Jurkat T cells and MCF-7 carcinoma cells. Like BAFF, APRIL also stimulates the proliferation of B and T cells. The human APRIL gene codes for at least four alternatively spliced transcriptional variants, which give rise to different isoforms of the APRIL precursor protein. All isoforms can be cleaved by the protease, furin, to release a soluble C-terminal fragment, which comprises the TNF-like receptor binding of the APRIL precursor. Recombinant Murine APRIL is a soluble 21.9 kDa protein, consisting of 192 amino acid residues.