APRIL, a member of the TNF superfamily, is expressed in monocytes, macrophages, certain transformed cell lines, certain cancers of colon, and lymphoid tissues. APRIL, along with another TNF family member, BAFF, compete for two receptors, TACI and BCMA. ARPIL 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 human APRIL is a soluble 16.3kD protein, consisting of 146aa.