NEONATAL MYASTHENIA-GRAVIS AND THE ROLE OF AGALACTOSYL IGG

Neonatal autoimmune diseases are thought to be due to the transfer of maternal autoantibodies. However, there is a puzzling lack of correlat ion between maternal autoantibody titres and disease in the neonate. S o far, no factor reliably predictive of neonatal disease has been Foun d. Agalactosyl IgG is a variable feature of normal IgG. Preliminary st udies indicated that the percentage of agalactosyl IgG is lower in the serum of normal neonates, than in the serum of the mother at delivery . Since raised % agalactosyl IgG is often associated with autoimmune d isease we sought to determine whether this relationship holds true in a neonatal autoimmune disease. We measured the % agalactosyl IgG in pa ired maternal-cord sera from patients with myasthenia gravis, some of whom had offspring with neonatal myasthenia gravis. We found that the percentage of agalactosyl IgG was significantly higher in affected tha n in unaffected neonates. Moreover % agalactosyl IgG was higher in ser a of affected neonates than in serum from their mothers, while unaffec ted infants of mothers with myasthenia had %Gal(0) lower than their mo thers, mimicking the normal situation. This suggests that in affected neonates a high proportion of the IgG is synthesised by the baby itsel f rather than derived from the mother. This agrees with previous evide nce based on the presence of idiotypes not found in the mother which i mplied that the neonates with neonatal myasthenia gravis produce their own autoantibodies.