PE-Labeled Monoclonal Anti-Human 4-1BB Antibody, Mouse IgG1 (0.03% Proclin)

4-1BB, also known as CD137 and TNFRSF9, is an approximately 30 kDa transmembrane glycoprotein in the TNF receptor superfamily. 4-1BB functions in the development and activation of multiple immune cells. Mature human 4-1BB consists of a 163 amino acid (aa) extracellular domain (ECD) with four TNFR cysteine-rich repeats, a 27 aa transmembrane segment, and a 42 aa cytoplasmic domain . Within the ECD, human 4-1BB shares 60% aa sequence identity with mouse and rat 4-1BB. 4-1BB is expressed as a disulfide-linked homodimer on various populations of activated T cell including CD4, CD8, memory CD8, NKT, and regulatory T cells as well as on myeloid and mast cell progenitors, dendritic cells, mast cells, and bacterially infected osteoblasts . It binds with high affinity to the transmembrane 4-1BB Ligand/TNFSF9 which is expressed on antigen presenting cells and myeloid progenitor cells . This interaction costimulates the proliferation, activation, and/or survival of the 4-1BB expressing cell . It can also enhance the activation-induced cell death of repetitively stimulated T cells . Mice lacking 4-1BB show augmented T cell activation, perhaps due to its absence on regulatory T cells . 4-1BB can associate with OX40 on activated T cells, forming a complex that responds to either ligand and inhibits Treg and CD8 T cell proliferation . Reverse signaling through 4-1BB Ligand inhibits the development of dendritic cells, B cells, and osteoclasts but supports mature dendritic cell survival and costimulates the proliferation and activation of mast cells. 4-1BB activation enhances CD8 T cell and NK cell mediated anti-tumor immunity . It also contributes to the development of inflammation in high fat diet-induced metabolic syndrome . Soluble forms of 4-1BB and 4-1BB Ligand circulate at elevated levels in the serum of rheumatoid arthritis and hematologic cancer patients, respectively .