Human TNF RI/TNFRSF1A Antibody

TNF receptor 1 (TNF RI; also called TNF R-p55/p60 and TNFRSF1A) is a type I transmembrane protein member of the TNF receptor superfamily member, designated TNFRSF1A (1, 2). Both TNF RI and TNF RII (TNFRSF1B) are widely expressed and contain four TNF-  alpha trimer-binding cysteine-rich domains (CRD) in their extracellular domains (ECD). However, TNF RI is thought to mediate most of the cellular effects of TNF-alpha (3). It is essential for proper development of lymph node germinal centers and Peyer’s patches, and for combating intracellular pathogens such as Listeria (1 - 3). TNF RI is also a receptor for TNF-beta /TNFSF1B (lymphotoxin-alpha) (4). TNF RI is present on the cell surface as a trimer of 55 kDa subunits (4, 5). TNF-alpha induces sequestering of TNF RI in lipid rafts, where it activates NF kappaB and is cleaved by ADAM-17/TACE (9, 10). Release of the 28 - 34 kDa TNF RI ECD also occurs constitutively and in response to products of pathogens such as LPS, CpG DNA or S. aureus protein A (1, 6 - 8). Full-length TNF RI may also be released in exosome-like vesicles (11). Release helps to resolve inflammatory reactions, since it down-regulates cell surface TNF RI and provides soluble TNF RI to bind TNF-alpha (6, 12, 13). Exclusion from lipid rafts causes endocytosis of TNF RI complexes and induces apoptosis (1). Human TNF RI is a 455 amino acid (aa) protein that contains a 21 aa signal sequence, a 190 aa ECD with a PLAD domain(5) that mediates constitutive trimer formation, followed by the four CRD, a 23 aa transmembrane domain, and a 221 aa cytoplasmic sequence that contains a neutral sphingomyelinase activation domain and a death domain (15). The ECD of human TNF RI shows 80%, 80%, 73%, 69% and 70% aa identity with dog, cat, pig, rat and mouse TNF RI, respectively; it shows 23% aa identity with the ECD of TNF RII.