Human CD27/TNFRSF7 APC-conjugated Antibody

Human CD27 is a 50-55 kDa lymphocyte-specific member of the TNF receptor superfamily. CD27 is expressed on a subset of human thymocytes as well as NK cells, B cells, and CD4⁺ and CD8⁺ T cells. CD27 expression is up-regulated after TCR stimulation. Within the CD4⁺ compartment, it is preferentially expressed on CD45RA⁺ cells. In contrast, it is preferentially expressed on CD45RO⁺ cells in the CD8⁺ compartment. CD27 also appears to be a potential marker for memory B cells. It exists as both a disulfide-linked dimer on the cell surface and as a soluble 32 kDa protein found in serum. Human CD27 is a 260 amino acid (aa) protein with a 19 aa signal, a 173 aa extracellular domain, a 21 aa transmembrane domain, and a 48 aa cytoplasmic domain. The ligand for CD27 is CD70. CD70 is expressed on thymic stromal cells and multiple activated leukocytes including NK cells, CD4⁺ and CD8⁺ T cells, and gamma delta T cells. Additionally a subset of activated B cells express CD70. The CD27/CD70 interaction appears to be a weak costimulatory pathway involved in T cell and B cell immune response. CD27/CD70 interactions may be more involved in controlling the expansion phase of an immune response. This would be in contrast to B7/CD28 interactions, which are important for the activation phase of immune responses. Over aa 21-192, human and mouse CD27 share 60% aa sequence identity.