Analysis Note

The biological activity is measured in a cytotoxicity assay using the TNF-suspectible murine L929 cell line in the presence of actinomycin D.

Biochem/physiol Actions

Tumor necrosis factor-β (TNF-β), also known as lymphotoxin-α (LT-α) and cytotoxic factor, is a 25 kDa glycoprotein that is tightly regulated by lymphocytes. TNF-β and TNF-α share a 28% amino acid sequence identity, and as soluble forms, both can exist in solution as homotrimers, activate the same TNF receptors (TNFR1 and TNFR2) and elicit many of the same bioactivities. Unlike TNF-α, TNF-β can also form heterotrimers with one or two molecules of the related membrane-bound lymphotoxin-β (LT-β). Reportedly, LTα1/β2, the predominant heterotrimer, binds and activates only the LT-β receptor, LT-βR. The other heterotrimer, LT-α2/β1 binds and activates TNFR1 and TNFR2 but not LT-βR. TNF-β is expressed in activated T, B and NK cells and in certain transformed cells. Genes for TNF-β, LT-β and TNF-α are tightly linked near each other within the MHC. TNF-β appears to play many of the same biological roles as TNF-α, but the membrane-bound form with LT-β is critical for normal lymphoid organ development. Genetic polymorphisms in TNF-α and TNF-β have been linked to certain pathological conditions, including myasthenia gravis. At the amino acid level, human and mouse TNF-β are 74% homologous and human and mouse LT-β are 80% homologous.

Physical form

lyophilized from a 0.2 µm filtered solution in PBS with BSA as a carrier protein