Autoantibodies from Mothers of Children with Congenital Heart Block Downregulate Cardiac L-type Ca Channels

Congenital heart block (CHB) affects offspring of mothers with autoantibodies (positive IgG) to intracellular SSA/Ro and SSB/La ribonucleoproteins and is associated with high morbidity and mortality. Here, we show that maternal anti-Ro/La antibodies immunoreact with human fetal cardiomyocyte sarcolemma, recognize human L-type Ca channelα1C -protein and functionally inhibit expressed current in oocytes injected withα1C cRNA and Purkinje L-type Ca current. Furthermore, cardiac myocytes from pups born to SSA/Ro-immunized mice exhibited reduced L-type Ca current density. All together, the data establish that L-type calcium channel is a target for maternal antibodies and may provide a functional basis for the electrocardiographic abnormalities seen in infants with CHB.