SUBCLASS DISTRIBUTION OF MATERNAL AND NEONATAL ANTI-RO(SSA) AND LA(SSB) ANTIBODIES IN CONGENITAL HEART-BLOCK

Objective. To compare the subclass distribution of anti-48 kDa La(SSB) and anti-52 and 60 kDa Ro(SSA) antibodies in the maternal and neonata l circulation, in pregnancies affected and unaffected by the developme nt of congenital heart block (CHB). Methods. Sera were obtained from 3 2 mothers (during 34 pregnancies, 23 complicated by CHB and 11 healthy ) demonstrated to have anti-Ro(SSA) and/or La(SSB). Maternal and neona tal autoantibodies were evaluated for subclass distribution by ELISA. Results. All 4 subclasses of anti-Ro(SSA) and La(SSB) antibodies cross the placenta and are detectable in sera obtained from the umbilical c ord. IgG1 and IgG3 were the major subclasses represented in the 48 kDa La(SSB) and 52 kDa Ro(SSA) responses. All subclasses, including IgG2 and IgG4, were observed in about one-third of the anti-52 kDa Ro(SSA) and 48 kDaLa(SSB) responses. In contrast, anti-60 kDa antibodies were, with rare exception, confined to IgG1. Except for anti-48 kDa La(SSB) IgG3 antibodies, no significant differences were observed between aff ected and unaffected pregnancies in the ratio of maternal to neonatal levels of any of the antibody subclasses. Overall, there were no signi ficant differences in the subclass profiles between mothers whose chil dren had heart block and those who did not. Conclusion. The IgG subcla sses of anti-48 kDa La(SSB) and anti-52 and 60 kDa Ro(SSA) do not acco unt for the susceptibility of one fetus versus another for the develop ment of CHB. Anti-60 kDa Ro(SSA) antibodies are more restricted in sub class distribution than anti-52 kDa Ro(SSA) or 48 kDa La(SSB) response s.