Detection of autoantibodies to Ro(SS-A), La(SS-B) and U sub(1)RNP in different congenital heart rhythm disorders using immunoblot and enzyme immunoassay

The aim of the study was to determine if autoantibodies have distinctive qualitative or quantitative characteristics in children with congenital heart rhythm disorders compared to unaffected infants. Sera of fifty-three infants with different heart rhythm disorders and eight unaffected children born to SLE mothers were tested for antibodies to Ro(SS-A), La(SS-B) and U sub(1)RNP (including recombinant A-, C-, 68 kD-proteins) using enzyme immunoassays and immunoblot. 21 sera from affected and 8 sera from healthy children reacted in counter-immunoelectrophoresis with Ro(SS-A). 8/8 infants with third degree atrioventricular (AV)-block, 4/8 with first degree AV-block, one with sinusbradyarrhythmia (SB) and another with SB/first degree AV-block were anti-52 kD Ro(SS-A) positive compared to 7/8 healthy infants. Infants with third degree AV-block had significantly higher anti-52 kD Ro(SS-A) levels than those with the milder heart rhythm disorders and the healthy group. Anti-La(SS-B) antibodies were detected significantly and in significantly higher titres in AV III than in other types of congenital heart block. Anti-U sub(1)RNP-68 kD antibodies were positive in 3/8 healthy, 2/8 first degree AV-block and in 1/8 third degree AV-block cases. Third degree AV-block was more frequently found in female infants. It was concluded that the influence of antibody levels to the 52 kD Ro(SS-A) and La(SS-B) components and the association of anti-52 kD Ro(SS-A), La(SS-B) and -60 kD Ro(SS-A) antibodies, as well as the sex, on the severity of congenital AV-conduction defects suggests involvement of these factors in the pathogenesis of these disorders.