CD5 is a type I transmembrane glycoprotein receptor and member of the scavenger receptor cysteine-rich (SRCR) superfamily.1 It is composed of three extracellular cysteine-rich domains, a transmembrane region, and a cytoplasmic tail containing an imperfect immunoreceptor tyrosine-based activating motif (ITAM). CD5 is expressed at differing levels on mature CD4+ and CD8+ T cells and thymocytes, and at lower levels on B1a cells and B cell chronic lymphocytic leukemia (B-CLL) cells.2 It acts a negative regulator of T cell signaling, despite the presence of an ITAM, and has a role in promoting the survival of thymocytes and mature T cells. CD5+ B cells are at their highest levels during development, lowest during early adulthood, and increase in middle-to-late adulthood, a change that correlates with an increased incidence of B-CLL and mantle cell lymphoma (MCL).3 CD5+ B cells primarily have a follicular mantle phenotype and produce low affinity polyreactive antibodies. CD5 expression on T cells protects against experimental autoimmune encephalomyelitis (EAE) in mice, but the levels of CD5+ B cells are increased in patients with systemic lupus erythematosus (SLE).4,5 CD5 has a complex role in cancer, with high levels of CD5 on tumor-infiltrating T cells (TILs) protecting TILs from apoptosis, but reduced CD5 levels on TILs enhancing CD8+ T cell-mediated lysis of malignant cells.4 CD5 has commonly been used as a marker of T cells, B1a cells, and B-CLL cells.2 Cayman’s CD5 (C-Term) Rabbit Monoclonal Antibody (Clone RM314) can be used for immunohistochemistry (IHC) and Western blot (WB) applications.WARNING This product is not for human or veterinary use.
