Neonatal lupus and congenital complete heart block: manifestations of passively acquired autoimmunity.

The neonatal lupus syndromes, which comprise transient hematologic and cutaneous disorders as well as the permanent manifestation of heart block, are considered to result from injury by passively acquired maternal autoantibodies. The active placental transport of maternal IgG antibodies becomes operative late in the second trimester coincident with the time at which bradycardia and myocarditis become evident. Surprisingly there are no clinically detectable abnormalities in the maternal hearts. The recognition that antibodies to the SSA/Ro-SSB/La ribonucleoprotein complex were found in 85% of sera from mothers of offspring with neonatal lupus was an important advance and directed attention to these antigens as potential candidates despite their intracellular location. In the present review we describe an experimental approach to the treatment of a fetus diagnosed by in utero echocardiogram to have congenital complete heart block and to the prevention of this condition in an at-risk pregnancy. In an attempt to more specifically define the relevant antigen-antibody systems involved in the pathogenesis of neonatal lupus we have utilized the technique of immunoblot to evaluate sera from mothers of offspring with permanent manifestations of neonatal lupus including heart block and hepatic fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)