Circulating immune complexes in infants fed on cow's milk

Delire et al. have reported antigen-antibody (Ag-Ab) complexes in newborns, fed on cow's milk, 6 days after birth, whereas they were absent from breast-fed neonates. The method they used was the inhibition of latex-IgG agglutination by polyclonal rheumatoid factor (pRF), linked to the Ag-Ab complexes. The presence of immune complexes was attributed to the passage through the placenta of maternal IgG with antibody activity against proteins in cow's milk. This interpretation was also based on the characterization of the Ag-Ab nature of the immune complex-like material. We have now used the same and a different method to study a similar population of newborns. Our results are very different from those of Delire et al. We conclude that the possible pathogenicity of immune complexes cannot be assessed on the basis of a single insensitive test and in the absence of symptoms of serum sickness.