Humoral immunity in congenital rubella.

1. Rubella complement-fixing (CF) and neutralizing antibodies are reported for eighty-one patients with congenital rubella, six adults with acute rubella, and a control series of fifty-four children. In some of the congenital rubella patients virus isolation and serum immunoglobulin levels are recorded, together with maternal antibody and immunoglobulin levels. 2. In children infected with rubella in utero (with neutralizing antibody), the incidence and titres of CF antibody are significantly higher in those with defects than those without defects. 3. Whereas neutralizing antibody persists in congenital rubella and is probably a combination of IgG produced by both mother and child, and IgM produced by the child alone, CF antibody presents a more complex picture. It is nearly always detectable at some time in patients with congenital rubella, but may show a rising, falling or constant titre. The titre correlates significantly with the IgG concentration, and this and other data suggest that it may be predominantly IgG produced by both mother and child. 4. There is no obvious relationship between virus elimination and either CF or neutralizing antibodies or levels of IgG or IgM.