The TNF-beta Leeporter™ Luciferase Reporter cell line is a stably transfected RAW264.7 cell line which expresses Renilla luciferase reporter gene under the transcriptional control of the TNF-beta promoter. Tumor necrosis factor-beta (TNF-beta) one of the major proinflammatory cytokines, which is produced predominantly by mitogen-stimulated T lymphocytes and leukocytes. TNF-beta is involved in the regulation of various biological processes such as cell proliferation, differentiation and apoptosis. TNF-beta gene polymorphisms are also significantly associated with disease susceptibility and phenotype in patients with psoriatic arthritis. The TNF-beta induction by lipopolysaccharide (LPS), the Toll-like receptor 4 (TLR4) ligand, is shown in Figure 1.