Gm and Inv allotypes in premature infants.

Using haemagglutination inhibition tests specific for Gm allotypes and similar tests for IgG4, the placental transfer of the four IgG subclasses from mother to foetus has been confirmed. The Gm phenotype of a cord serum is often identical to that in the corresponding maternal serum. However in 31 cases out of the 90 tested, Gm allotypes were present in the cord serum that were not present in the maternal serum. These allotypes produced by the foetus in utero are dependent on a paternal gene. The logarithm of the IgG level increase proportionately with gestational age (r = 0.59 p less than 0.001).