title: Evidence for a light chain restriction of glycoprotein Ib/IX and IIb/IIIa reactive antibodies in chronic idiopathic thrombocytopenic purpura (ITP).
abstract: To address the assumption of clonally restricted antibodies in immune thrombocytopenias we studied sera from 19 patients with chronic ITP known to possess antibodies reactive with glycoprotein (GP) Ib/IX and/or GPIIb/IIIa. These sera were re-analysed using the standard monoclonal antibody immobilization of platelet antigens (MAIPA) assay and 16 patients exhibited IgG antibodies reactive with GPIIb/IIIa; seven patients showed also a reactivity with GPIb/IX. Employing a light-chain-specific MAIPA assay, 75% (12/16) of these sera displayed GPIIb/IIIa-specific antibodies that were light chain restricted; only 13% (2/16) of the GPIIb/IIIa reactive sera showed a mixed kappa and lambda phenotype. A light-chain-restricted phenotype was also seen for the GPIb/IX reactive antibodies. To further substantiate these findings, the MAIPA assay was modified in order to avoid interference from human anti-mouse antibodies. A high frequency of light-chain restricted platelet antibodies was also found using the modified MAIPA technique. These results support the hypothesis of a clonal B-cell expansion in immune thrombocytopenias, producing antibodies with a restricted idiotype repertoire and reacting with a limited number of epitopes.
authors.affiliation: Department of Medicine, Sahlgrenska Hospital, University of Göteborg, Sweden.
authors.forename: D
authors.initials: D
authors.lastname: Stockelberg
authors.forename: M
authors.initials: M
authors.lastname: Hou
authors.forename: S
authors.initials: S
authors.lastname: Jacobsson
authors.forename: J
authors.initials: J
authors.lastname: Kutti
authors.forename: H
authors.initials: H
authors.lastname: Wadenvik
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000276:immunology*; D002999:Clone Cells / Q000276:immunology; D005260:Female; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000276:immunology*; D007145:Immunoglobulin kappa-Chains / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010980:Platelet Membrane Glycoproteins / Q000276:immunology*; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains; D010980:Platelet Membrane Glycoproteins