Figure 1. Placental transport of IgG subclasses is more efficient for IgG1 and IgG4 than for IgG2 and IgG3.

Blood was collected from mothers just before or after birth and from neonates birth. A) Transport rates for all IgG subclasses expressed as cord/maternal ratios found at birth. The transport rates differed significantly from each other (P<0.0001), except for IgG2 and IgG3 (not significant), as tested by one-way Anova and Tukey's multiple comparison test. (B–E)IgG subclass 1–4 serum levels were quantified by nephelometry and each pair was plotted on a X axis displaying days of each pregnancy against IgG concentration. Average neonate concentration was significantly higher than in the mother for IgG1 and IgG4 as tested by a paired-T test as shown (child/mother ratio = 1.55 and 1.38, respectively) while averge concentrations for IgG2 and IgG3 were not significantly different in mothers and their children (child/mother ratios not significantly different from 1). One pre-term baby was identified displaying low transport of all IgG (square symbol). (F) Child/mother transport ratio of subclasses IgG2-4 for each pair was plotted relative to the IgG1 transport ratios.