High galactosylation of oligosaccharides in umbilical cord blood IgG, and its relationship to placental function.

N-linked oligosaccharides on human serum IgGs have been reported to modulate IgG function. We studied umbilical cord blood to determine whether neonatal IgGs have characteristic structures related to developmental and pathological status. Oligosaccharide patterns of serum IgG from 45 umbilical cord blood samples were characterized by HPLC, and compared with those of serum IgG from 11 normal adults. Oligosaccharyl amines from purified IgG were released by recombinant N-glycanase, labeled with fluorescence reagent FMOC (9-fluorenylmethyl chloroformate), and analyzed quantitatively by high-pressure liquid chromatography (HPLC). Increased galactosylation was observed in cord blood. The ratio of galactosylated to non-galactosylated oligosaccharides on IgG was 7.90+/-3.92 (mean+/-S.D.) in cord blood, significantly higher than the ratio in adults (1.60+/-0.62, P<0.0001). There were weak but not significant correlations between the ratio and birth weight, gestation period, mother's age, and no correlation with serum IgG concentration. The ratio was lower for premature or intra-uterine growth retarded neonates. Our results, in conjunction with previous reports that galactosylated IgG stimulates Fc-mediated phagocytosis of monocytes, suggest that increased galactosylation of IgG enhances neonatal immunity.