Mouse 4‑1BB/TNFRSF9/CD137 Antibody

4-1BB, also known as CD137 and ILA (induced by lymphocyte activation), is a TNF receptor superfamily member and has been designated TNFRSF9. Mouse 4-1BB cDNA encodes a 256 amino acid (aa) residues type I transmembrane protein with a putative 23 aa signal peptide, a 164 aa extracellular domain, a 21 aa transmembrane domain and a 48 aa cytoplasmic region (1 - 3). A soluble 4-1BB is released from surfaces of cells expressing the transmembrane protein (4). Mouse 4‑1BB shares approximately 60% aa sequence identity with its human counterpart. 4-1BB is expressed on activated CD4⁺ and CD8⁺ T cells, thymocytes, and NK cells. It is also expressed on monocytes, neutrophils, DCs and eosinophils (5). The ligand for 4-1BB (4-1BBL), also named TNFSF9, belongs to the TNF ligand superfamily. 4-1BBL is predominantly expressed on activated antigen presenting cells (APCs) such as B cells, macrophages and dendritic cells (DCs). It is also expressed on most T and B lymphoma cell lines. In response to 4-1BBL binding, 4-1BB transduce a T cell costimulatory signal in both CD4⁺ and CD8⁺ T cells to promote survival and enhance proliferation, cytokine production and effector function. In vivo, the costimulatory activity of 4-1BB has been shown to be important in graft-vs-host disease and antiviral CTL responses. On dendritic cells, 4-1BB is a DC-activating molecules that enhances cytokine production and upregulates expression of B7-1 and B7‑2 costimulatory molecules, resulting in an improved ability to stimulate T cell responses (1 - 5).