TRANSFER OF IGG SUBCLASSES ACROSS PLACENTA IN TERM AND PRETERM NEWBORNS

In order to study placental transfer of IgG subclasses, paired blood s amples were collected from mothers and umbilical cord of preterm (N = 69) and full-term (N = 68) newborns. The full-term group was further d ivided into 3 subgroups: appropriate for gestational age (AGA, N = 43) , large for gestational age (LGA, N = 13) and small for gestational ag e (SGA, N = 12), according to birth weight. IgC subclasses (IgG1, IgG2 , IgG3 and IgG4) were measured by the single radial immunodiffusion te chnique using monoclonal antibodies. IgG1 and IgG3 newborn subclass co ncentrations (10.17 and 0.57 g/l, respectively) increased with increas ing gestational age and reached maternal levels (IgG1 = 8.86; IgG3 = 0 .67 g/l) during the 37th week of pregnancy. Low levels of these subcla sses were found in premature newborns. IgG2 from newborns were always lower than maternal levels (P<0.05). LGA and SGA newborns had equivale nt levels of IgG1 and IgG2 compared with AGA. SGA newborns had higher levels of lgG3 and lower levels of IgG4 than LGA and AGA newborns.