title: SR-Ca2+ ATPase as an autoimmunogen in experimental myocarditis.
abstract: The concept of autoimmunity in the pathogenesis of myocarditis or dilated cardiomyopathy is gaining impetus. Since systolic functional impairment and subsequent recovery are frequently observed in myocarditis, we reasoned that the development of autoimmunity to cardiac sarcoplasmic reticulum calcium ATPase (SR-Ca2+ ATPase), which could interfere with intracellular calcium regulation and therefore affect myocardial contractility, should lead to immune-mediated myocarditis in experimental animals. Murine monoclonal antibody 4C11-20.21 (IgM class) generated against canine cardiac SR-Ca2+ ATPase inhibits the cardiac but not the skeletal ATPase activity. Immunization of CAF1/J mice with 4C11-20.21-affinity-column-purified cardiac SR-ATPase produced a time-dependent induction of myocardial injury consistent with the diagnosis of myocarditis. Furthermore, the antibody 4C11-20.21 alone can induce myo-necrosis in severe combined immunodeficiency (SCID) mice indicating a mechanism of cardiomyopathy independent of the cytotoxic T-cell mediated autoimmunopathy. Administration of 4C11-20.21 into immunocompetent CAF1/J mice resulted in minimal myocardial abnormality (40% with perivascular and/or interstitial mononuclear lymphoplasmacytoid aggregates, 10% with borderline myocarditis and 10% with lesions consistent with focal myocarditis). All control animals had normal hearts. Immunoperoxidase electron microscopic examination of the involved cardiac tissues showed antibody localization in the subsarcolemmal myotubular system and focal staining of the immediately adjacent sarcolemma in mice injected with 4C11-20.21 but not with 2C12.1B5. The time-dependent association between cardiac SR-Ca2+ ATPase administration and development of myocardial lesions, as well as potentiated induction of myonecrosis with anti-cardiac SR-Ca2+ ATPase antibody in SCID relative to immunocompetent mice, suggest a potential autoimmunopathogenic role of cardiac SR-Ca2+ ATPase in experimental myocarditis.
authors.affiliation: Center for Drug Targeting and Analysis, Bouve College of Pharmacy and Health Sciences, Northeastern University, Boston, MA 02115, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Khaw
authors.forename: J
authors.initials: J
authors.lastname: Narula
authors.forename: A R
authors.initials: AR
authors.lastname: Sharaf
authors.forename: P D
authors.initials: PD
authors.lastname: Nicol
authors.forename: J F
authors.initials: JF
authors.lastname: Southern
authors.forename: M
authors.initials: M
authors.lastname: Carles
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001324:Autoantigens / Q000276:immunology*; D001327:Autoimmune Diseases / Q000276:immunology* / Q000473:pathology; D000252:Calcium-Transporting ATPases / Q000276:immunology*; D002311:Cardiomyopathy, Dilated / Q000276:immunology* / Q000473:pathology; D004285:Dogs; D005260:Female; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D016513:Mice, SCID; D009200:Myocardial Contraction / Q000276:immunology; D009205:Myocarditis / Q000276:immunology* / Q000473:pathology; D009206:Myocardium / Q000276:immunology / Q000473:pathology; D012519:Sarcoplasmic Reticulum / Q000276:immunology* / Q000473:pathology
chemical_list: D000911:Antibodies, Monoclonal; D001324:Autoantigens; D000252:Calcium-Transporting ATPases