PLACENTAL-TRANSFER FAVORS HIGH AVIDITY IGG ANTIBODIES

The aim of the present study was to evaluate if maternal-foetal antibo dy placental transfer may be affected by antibody avidity. We compared the avidity index (AI) of IgG antibodies to tetanus toroid (TT) and t o type 3 pneumococcal antigen (Pn) in cord blood of 10 healthy term an d 8 preterm infants and in their mothers' sera at delivery. In order t o evaluate whether a heavier antigenic exposure may influence the plac ental transfer, we also studied 15 Pakistani maternal sera and cord bl ood pairs. TT-and Pn-specific antibody AI was significantly higher in Italian and Pakistani term infants than in their mothers, while a sign ificant difference in specific TT antibody AI, but not in specific Pn antibody Al was observed between preterm infants and their mothers. It alian and Pakistani cord blood/maternal serum pairs showed comparable values of AI. Our data suggest that high avidity antibodies preferenti ally cross the placenta; this seems to start early during gestation an d appears to be related to the nature of the antigen to which the anti bodies are directed, but not to the degree of antigenic exposure.