title: Changes in CD45 isoform expression accompany antigen-induced murine T-cell activation.
abstract: Leukocytes express a family of plasma membrane proteins called CD45 or the leukocyte common antigen. Isoforms of various molecular masses, 180-240 kDa, are produced by alternative splicing and usage of three exons, named A, B, and C, that encode the N-terminal portion of the external domain. By using monoclonal antibodies that precipitate B exon-dependent and B exon-independent isoforms we find that both murine CD4+ and murine CD8+ T cells selectively down-regulate the B exon-dependent forms of CD45 during an immune response. This change was monitored by using fluorescence-activated cell sorter (FACS) analysis and immunoprecipitation from surface radioiodinated and metabolically labeled cells. The loss of the 190-kDa B exon-dependent isoform during T-cell activation is accompanied by an increased production of a 180-kDa form, which does not contain the B exon-encoded sequence. This accounts for our observation that the overall expression of CD45, as assessed by FACS analysis, does not change.
authors.affiliation: Laboratory of Cellular Physiology and Immunology, Rockefeller University, New York, NY 10021.
authors.forename: M L
authors.initials: ML
authors.lastname: Birkeland
authors.forename: P
authors.initials: P
authors.lastname: Johnson
authors.forename: I S
authors.initials: IS
authors.lastname: Trowbridge
authors.forename: E
authors.initials: E
authors.lastname: Puré
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation / Q000032:analysis / Q000235:genetics / Q000276:immunology*; D005091:Exons; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006649:Histocompatibility Antigens / Q000032:analysis / Q000235:genetics / Q000276:immunology*; D017493:Leukocyte Common Antigens; D008198:Lymph Nodes / Q000276:immunology; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D008815:Mice, Inbred Strains; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D006649:Histocompatibility Antigens; D008562:Membrane Glycoproteins; D017493:Leukocyte Common Antigens