title: CD45 isoforms in T cell signalling and development.
abstract: The CD45 phosphotyrosine phosphatase is expressed on T cells as multiple isoforms due to alternative splicing. The panoply of isoforms expressed is tightly regulated during T cell development and on mature peripheral T cell subsets following activation. We describe the analysis of comparative CD45 isoform expression levels on thymic and T cell subsets from the C57BL/6 mouse. Only four isoforms were expressed at significant protein levels: CD45R0, CD45RB, CD45RBC and CD45RABC, although trace amounts of others may be present. The expression of CD45RBC was about nine-fold higher on CD8(+) than on CD4(+) peripheral T cells, whereas CD45R0 expression was higher on CD4(+) T cells. We provide a general overview of the current models that have been proposed to explain the molecular actions of the different CD45 isoforms. Achieving a thorough understanding of the biological reasons for the existence and tight regulation of CD45 isoform expression in immune cells remains one of the outstanding challenges in the CD45 research field.
authors.affiliation: Laboratory of Lymphocyte Signalling and Development, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK.
authors.forename: Louise
authors.initials: L
authors.lastname: McNeill
authors.forename: Robin L
authors.initials: RL
authors.lastname: Cassady
authors.forename: Samiramis
authors.initials: S
authors.lastname: Sarkardei
authors.forename: Joanne C
authors.initials: JC
authors.lastname: Cooper
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Morgan
authors.forename: Denis R
authors.initials: DR
authors.lastname: Alexander
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000276:immunology* / Q000502:physiology; D005434:Flow Cytometry; D017493:Leukocyte Common Antigens / Q000235:genetics* / Q000276:immunology / Q000502:physiology; D051379:Mice; D008954:Models, Biological; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000502:physiology; D015398:Signal Transduction / Q000276:immunology* / Q000502:physiology; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000502:physiology; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology / Q000502:physiology
chemical_list: D020033:Protein Isoforms; D017493:Leukocyte Common Antigens