title: Identification of a candidate CD5 homologue in the amphibian Xenopus laevis.
abstract: We identified a novel T cell Ag in the South African clawed toad (Xenopus laevis) by a mAb designated 2B1. This Ag is present in relatively high levels on most thymocytes, approximately 65% of splenocytes, 55% of PBL, and 65% of intestinal lymphocytes, but is rarely seen on IgM+ B cells in any of these tissues. Lymphocytes bearing the 2B1 Ag proliferate in response to stimulation with Con A or PHA, whereas the 2B1- lymphocytes are reactive to LPS. Biochemical analysis indicates that this Ag is a differentially phosphorylated glycoprotein of 71 to 82 kDa. The protein core of 64 kDa bears both N- and O-linked carbohydrate side chains. The amino-terminal protein sequence of the 2B1 Ag shares significant homology with both the macrophage scavenger receptor type 1 motif and the mammalian CD5/CD6 family. The biochemical characteristics and cellular distribution of the 2B1 Ag suggest that it represents the CD5 homologue in X. laevis. While T cells constitutively express this highly conserved molecule, Xenopus B cells acquire the CD5 homologue only when they are stimulated in the presence of T cells.
authors.affiliation: Department of Medicine, University of Alabama at Birmingham 35294, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Jürgens
authors.forename: L A
authors.initials: LA
authors.lastname: Gartland
authors.forename: L
authors.initials: L
authors.lastname: Du Pasquier
authors.forename: J D
authors.initials: JD
authors.lastname: Horton
authors.forename: T W
authors.initials: TW
authors.lastname: Göbel
authors.forename: M D
authors.initials: MD
authors.lastname: Cooper
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018956:CD5 Antigens / Q000235:genetics / Q000302:isolation & purification*; D002454:Cell Differentiation; D002460:Cell Line; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation / Q000276:immunology; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000276:immunology; D010835:Phytohemagglutinins / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000737:chemistry* / Q000276:immunology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014982:Xenopus laevis / Q000276:immunology*
chemical_list: D018956:CD5 Antigens; D010835:Phytohemagglutinins; D013755:Tetradecanoylphorbol Acetate