title: Cytotoxic mAb from rheumatic carditis recognizes heart valves and laminin.
abstract: Anti-streptococcal antibodies cross-reactive with N-acetyl-betaD-glucosamine (GlcNAc) and myosin are present in the sera of patients with rheumatic fever (RF). However, their role in tissue injury is not clear. In this study, we show that anti-GlcNAc/anti-myosin mAb 3.B6 from a rheumatic carditis patient was cytotoxic for human endothelial cell lines and reacted with human valvular endothelium and underlying basement membrane. Reactivity of mAb 3.B6 with the valve was inhibited by human cardiac myosin > laminin > GlcNAc. The mAb 3.B6 epitopes were localized in fragments of human cardiac myosin, including heavy meromyosin (HMM), the S1 subfragment, and two light meromyosin (LMM) peptides containing amino acid sequences KEALISSLTRGKLTYTQQ (LMM 1) and SERVQLLHSQNTSLINQK (LMM 33). A novel feature of mAb 3.B6 was its reactivity with the extracellular matrix protein laminin, which may explain its reactivity with the valve surface. A laminin A-chain peptide (HTQNT) that includes homology to LMM33 inhibited the reactivity of mAb 3.B6 with human valve. These data support the hypothesis that cross-reactive antibodies in rheumatic carditis cause injury at the endothelium and underlying matrix of the valve.
authors.affiliation: Department of Microbiology and Immunology, and. Department of Pediatric Cardiology, Children's Heart Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Galvin
authors.forename: M E
authors.initials: ME
authors.lastname: Hemric
authors.forename: K
authors.initials: K
authors.lastname: Ward
authors.forename: M W
authors.initials: MW
authors.lastname: Cunningham
mesh_terms: D000117:Acetylglucosamine / Q000276:immunology; D000293:Adolescent; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D004730:Endothelium, Vascular / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D006351:Heart Valves / Q000276:immunology*; D006801:Humans; D007797:Laminin / Q000276:immunology*; D008297:Male; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D009205:Myocarditis / Q000209:etiology / Q000276:immunology*; D009218:Myosins / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology; D012214:Rheumatic Heart Disease / Q000209:etiology / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D007797:Laminin; D010446:Peptide Fragments; D009218:Myosins; D000117:Acetylglucosamine