TNF-beta, also known as lymphotoxin-alpha (LTalpha) and TNF-alpha are two structurally and functionally related proteins that bind to the same cell surface receptors (TNF RI and TNF RII) and produce a vast range of similar, but not identical effects. Mature TNF-beta/LTalpha and TNF-alpha share approximately 35% protein sequence homology, and the biologically active secreted forms of both proteins are trimers. Human and mouse TNF-beta/LTalpha share approximately 74% homology in their amino acid sequence and exhibit cross-species activity. Soluble TNF-beta/LTalpha is a homotrimer in solution. Secreted TNF-beta/LTalpha also complexes with the membrane associated LTbeta/TNFSF3 to generate two types of heterotrimers, LTalpha1/beta2 and LTalpha2/beta1.