We recently reported that maternal sera containing antibodies against SSA/Ro and SSB/La ribonucleoproteins (positive IgG) inhibited L-type Ca current in isolated cardiac myocytes and induced sinus bradycardia in a murine model of CHB.
Congenital heart block (CHB), detected at or before birth in a structurally normal heart, is strongly associated with autoantibodies reactive with the intracellular soluble ribonucleoproteins 48kD SSB/La, 52kD SSA/Ro, and 60kD SSA/Ro.
Timed pregnant mice (n=54) were injected with a single intravenous bolus of purified IgG containing human anti-SSA/Ro and anti-SSB/La antibodies from mothers of children with CHB.
Perfusion of hearts with purified IgG (800 microg/mL), isolated from the serum of a mother with SSA/Ro and SSB/La antibodies whose child had CHB, resulted in bradycardia associated with 2:1 AV block.
Congenital heart block (CHB), associated with antibodies to SS-A/Ro and SS-B/La, is most often detected between 18 and 24 weeks of gestation, yet the maternal heart is unaffected.