Anti—Ro/SS‐a Antibodies in the Pathophysiology of Congenital Heart Block in Neonatal Lupus Syndrome, An Experimental Model

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Abstract
Objective. To determine whether anti—Ro/SS‐A antibodies selectively bind to neonatal cardiac cells and alter membrane repolarization.Methods. An in vitro electrophysiologic and immunocytochemical experimental model contrasting neonatal and rabbit cardiac tissue was employed.Results. Sera and IgG‐enriched fractions from anti—Ro/SS‐A antibody—positive mothers of infants with neonatal lupus erythematosus and congenital heart block bind to neonatal, rather than adult, rabbit cardiac tissue and alter the transmembrane action potential (i.e., inhibit repolarization). The additional presence of anti—La/SS‐B antibodies was not additive or synergistic for these immunocytochemical and electrophysiologic features. Sera containing other antibody specificities (i.e., anti—native DNA, cardiolipin, Sm, and nuclear RNP) failed to stain the neonatal cardiac tissue or produce alterations in membrane repolarization.Conclusion. Anti—Ro/SS‐A antibodies may play a pathophysiologic role in the development of congenital heart block in neonatal lupus.