Fluorescent anti-heart IgM and raised levels of serum IgM in newborns with congenital heart diseases.

Thirty-five per cent (13 of 37) of newborns, studied at less than 2 weeks of age, with congenital heart lesions, had abnormally high serum levels of both IgM (>20 mg/Ioo ml) and anti-heart IgM demonstrable by a fluorescent technique. An association between the raised serum IgM, reflecting in utero infection, and the congenital heart defects may be deduced. Possible explanations of the presence of anti-heart IgM in the sera of these newborns include modification of the antigenicity of the developing heart with teratogenic effect produced by the invading organism, but not the anti-heart IgM; and direct teratogenic influence of the anti-heart antibody offetal origin raised against both the invading organism and shared (or modified) antigens in the host.