title: Relevance of individual CD5 extracellular domains on antibody recognition, glycosylation and co-mitogenic signalling.
abstract: CD5 is a type I glycoprotein which modulates T- and B-cell receptor-mediated signals and is expressed by thymocytes, mature T cells and a subset of mature B cells. The extracellular region of CD5 is composed of three scavenger receptor cysteine-rich domains (D1, D2, D3) for which only limited functional and structural data are available. Using cell transfectants expressing ectodomain-deficient CD5 molecules or CD5 immunoglobulin fusion proteins, we analysed individual CD5 domains with respect to monoclonal antibody binding specificity, glycosylation, and co-mitogenic signalling. Our results show the presence of N-linked oligosaccharides on D1 and D2, but not on D3. D1, the most amino-terminal domain, is predicted to be the most appropriately placed domain for an interaction with a ligand. This domain is recognised by a large panel of well characterised CD5 mAbs, reflecting its higher immunogenicity. In an attempt to develop mAbs with specificity for the more conserved membrane-proximal domains, we generated a unique mAb, named 83-C4, whose binding mapped to D3. Co-stimulatory studies revealed no significant differences between anti-D1 and anti-D3 mAbs. The high interspecies conservation of D3 implies a conserved role of this domain in CD5 function and the 83-C4 mAb promises to be a valuable tool in exploring this.
authors.affiliation: Servei d'Immunologia, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clínic, Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Calvo
authors.forename: O
authors.initials: O
authors.lastname: Padilla
authors.forename: L
authors.initials: L
authors.lastname: Places
authors.forename: E
authors.initials: E
authors.lastname: Vigorito
authors.forename: J M
authors.initials: JM
authors.lastname: Vilà
authors.forename: R
authors.initials: R
authors.lastname: Vilella
authors.forename: J
authors.initials: J
authors.lastname: Milà
authors.forename: J
authors.initials: J
authors.lastname: Vives
authors.forename: M A
authors.initials: MA
authors.lastname: Bowen
authors.forename: F
authors.initials: F
authors.lastname: Lozano
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D018956:CD5 Antigens / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D000939:Epitopes / Q000276:immunology* / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D008934:Mitogens / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D018956:CD5 Antigens; D000939:Epitopes; D008934:Mitogens