title: The accessory molecules CD5 and CD6 associate on the membrane of lymphoid T cells.
abstract: CD5 and CD6 are closely related lymphocyte surface receptors of the scavenger receptor cysteine-rich superfamily, which show highly homologous extracellular regions but little conserved cytoplasmic tails. Both molecules are expressed on the same lymphocyte populations (thymocytes, mature T cells, and B1a cells) and share similar co-stimulatory properties on mature T cells. Although several works have been reported on the molecular associations and the signaling pathway mediated by CD5, very limited information is available for CD6 in this regard. Here we show the physical association of CD5 and CD6 at the cell membrane of lymphocytes, as well as their localization at the immunological synapse. CD5 and CD6 co-immunoprecipitate from Brij 96 but not Nonidet P-40 cell lysates, independently of both the co-expression of other lymphocyte surface receptors and the integrity of CD5 cytoplasmic region. Fluorescence resonance energy transfer analysis, co-capping, and co-modulation experiments demonstrate the physical in vivo association of CD5 and CD6. Analysis of T cell/antigen-presenting cells conjugates shows the accumulation of both molecules at the immunological synapse. These results indicate that CD5 and CD6 are structurally and physically related receptors, which may be functionally linked to provide either similar or complementary accessory signals during T cell activation and/or differentiation.
authors.affiliation: Servei d'Immunologia, Institut Clinic d'Infeccions i Immunologia, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clinic, Barcelona 08036, Spain.
authors.forename: Idoia
authors.initials: I
authors.lastname: Gimferrer
authors.forename: Montse
authors.initials: M
authors.lastname: Farnós
authors.forename: Maria
authors.initials: M
authors.lastname: Calvo
authors.forename: María
authors.initials: M
authors.lastname: Mittelbrunn
authors.forename: Carlos
authors.initials: C
authors.lastname: Enrich
authors.forename: Francisco
authors.initials: F
authors.lastname: Sánchez-Madrid
authors.forename: Jordi
authors.initials: J
authors.lastname: Vives
authors.forename: Francisco
authors.initials: F
authors.lastname: Lozano
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D001483:Base Sequence; D018956:CD5 Antigens / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D002478:Cells, Cultured; D002648:Child; D017931:DNA Primers; D004735:Energy Transfer; D005453:Fluorescence; D006801:Humans; D008213:Lymphocyte Activation; D011233:Precipitin Tests; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018956:CD5 Antigens; C062279:CD6 antigen; D017931:DNA Primers