Changes in Healthy Human IgG Fc-Glycosylation after Birth and during Early Childhood

Abstract

Glycosylation on the fragment crystallizable (Fc) region of immunoglobulin G (IgG) has a large influence on the interaction of the antibody with Fc gamma receptors (FcγRs). IgG consists of four subclasses that all have distinct affinities for the different FcγRs. Knowledge about the Fc-glycosylation in healthy human is valuable as reference for new biomarkers and in the design of biopharmaceuticals that rely on IgG Fc-glycosylation. Previously, subclass-specific characterization of IgG Fc-glycosylation was performed for healthy adults, pregnant women, and newborns. For young healthy children, however, the subclass-specific description of IgG Fc-glycosylation is still lacking. Therefore, we performed the IgG subclass-specific analysis of the Fc-glycosylation of 130 healthy humans between birth and 40 years of age, including 22 samples derived from the umbilical cords of newborns. The analysis was performed by a previously published matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF)-mass spectrometry (MS) workflow, including a derivatization step for the linkage-specific stabilization of sialic acids. The characterization revealed that when children start to produce their own IgG they have a decreased galactosylation, sialylation, and bisection and an increased fucosylation compared with newborns. During childhood, the fucosylation and sialylation decrease, whereas bisection increases and galactosylation stays constant.

The N-Glycosylation of Mouse Immunoglobulin G (IgG)-Fragment Crystallizable Differs Between IgG Subclasses and Strains

“…This latter finding might be related to the infrequent immunological challenges lab mice experience. The same phenomenon was observed before in very young children (aged between 0.3 and 4 years), showing low levels of afucosylated IgGs, which increased with age (and likely immunological challenges) (33). In addition, high levels of afucosylated antibodies were observed before in human on antigen-specific antibodies against, amongst others, HIV gp120, human platelet antigen and red blood cells (8–10).…”

“…The presence of afucosylated diantennaries, as well as that of a bisecting GlcNAc on the diantennaries, is well-known for human IgG-Fc (30, 33, 41, 42), but has not yet been reported in an Fc-specific way for mouse IgG before (23). Interestingly, we identified both afucosylation and bisection on all IgG subclasses.…”

“…Glycopeptide signals were corrected for the actual percentage of isotopic patter integrated, the included charge states were summed per analyte and absolute values were normalized to the total signal intensity per IgG subclass. For the in-depth analysis of compositional features, derived traits were calculated (Table S3 in Supplementary Material; (20, 33)).…”

Natural killer cell activation by respiratory syncytial virus‐specific antibodies is decreased in infants with severe respiratory infections and correlates with Fc‐glycosylation

“…In addition to antibody functionality, we assessed the glycosylation status of both the total antibody pool and the RSV‐specific antibodies. Glycosylation, including galactosylation, sialylation, fucosylation and bisection, is expressed as a percentage of the measured antibodies and varies within a certain (narrow) range depending on the specific modification, with subtle differences between maternal and infant antibodies . As expected, analysis of the total antibody pool revealed changes related to infant age, where especially galactosylation showed a strong negative correlation with age.…”

“…These observations are in line with the gradual replacement of maternal with infant antibodies. Altered glycosylation during pregnancy and preferential transplacental transfer result in increased IgG Fc‐galactosylation of maternal antibodies . In addition, like all adult antibodies, maternal antibodies have lower fucosylation (94%) compared to highly fucosylated infant antibodies, which reach adult levels around the age of 20 years …”