Tumor necrosis factor alpha (TNF-a) is an inflammatory cytokine secreted by macrophages, monocytes, neutrophils, T cells, and NK-cells following stimulation by bacterial lipopolysaccharide (LPS). TNF-a signal activation occurs through two receptors, TNFR1 and TNFR2. TNFR1 is expressed on most cell types, unlike TNFR2, which is expressed mainly on immune cells. TNF-a functions to stimulate phagocytosis in macrophages, chemoattract neutrophils, increase insulin resistance, and induce fever.
Bioactivity Assay:Cytolysis of mouse L929 cells in the presence of Actinomycin D; ED50 =0.05 ng/mL; Bioactivity =2.0 x 10^7 units/mg