title: PECAM-1-regulated signalling thresholds control tolerance in anergic transgenic B-cells.
abstract: Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1/CD31) is an immunoglobulin (Ig)-immunoreceptor tyrosine based inhibitory motif (Ig-ITIM) superfamily member that recruits and activates protein-tyrosine phosphatases, predominantly SHP-2 and to a lesser extent, SHP-1. Previously, we have shown that deletion of PECAM-1 results in a hyper-proliferative B-cell phenotype. We wanted to test whether the Ig-ITIM superfamily member, PECAM-1 maintains peripheral tolerance by regulating signalling thresholds of B-cells that control autoantibody production or relaxed negative selection of autoreactive B-cells in bone marrow. In order to address this issue, we utilised the classical model of lysozyme/immunoglobulin transgenic mouse model that defines thresholds for eliminating or inactivating self-reactive B-cells. In this study, we show that breeding of double transgenes: soluble hen egg lysozyme (HEL) and its corresponding high-affinity receptor (HEL-Ig) onto PECAM-1 null background resulted in a spontaneous loss of B-cell tolerance in vivo. The resultant PECAM-1(-/-) Dbl Tg mice displayed elevated levels of anti-HEL immunoglobulin M (IgM) antibodies in the serum compared to PECAM-1+/+ anergic counterparts. Dbl Tg B-cells lacking PECAM-1 showed enhanced B-cell proliferation and calcium flux responses to LPS, IL-4 alone, IgM cross-linking and IL-4 indicating augmentation of antigen-receptor signalling. Thus, PECAM-1 is important in maintaining peripheral tolerance in Dbl Tg B-cells.
authors.affiliation: Kronheimer Building, Burnet Institute incorporating the Austin Research Institute, Studley Road, Heidelberg, Victoria 3084, Australia.
authors.forename: Mae-Xhum
authors.initials: MX
authors.lastname: Wong
authors.forename: John D
authors.initials: JD
authors.lastname: Hayball
authors.forename: Denise E
authors.initials: DE
authors.lastname: Jackson
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001323:Autoantibodies / Q000276:immunology; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D001853:Bone Marrow / Q000276:immunology; D002118:Calcium / Q000276:immunology; D049109:Cell Proliferation / Q000187:drug effects; D003432:Cross-Linking Reagents / Q000494:pharmacology; D007108:Immune Tolerance; D007075:Immunoglobulin M / Q000494:pharmacology; D015847:Interleukin-4 / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D009113:Muramidase / Q000276:immunology / Q000494:pharmacology; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology*; D015398:Signal Transduction
chemical_list: D001323:Autoantibodies; D003432:Cross-Linking Reagents; D007075:Immunoglobulin M; D008070:Lipopolysaccharides; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D015847:Interleukin-4; C421864:hen egg lysozyme; D009113:Muramidase; D002118:Calcium