Table I. IgG Fab glycosylation: what is (un)known?
Structural knowledge
 Found in 15–25% of IgG(11, 12, 17)
 Highly processed complex-type biantennary N-linked glycans(1517)
 Occupancy and structure may vary with position(22, 23)
 Distinct patterns are associated with pathophysiological conditions(5, 15, 39, 40, 4346, 51)
Established activities
 Can influence Ag binding(18, 23, 50, 5456)
 Can affect in vivo Ab half-life(23)
 Can alter Ab stability and aggregation(52, 66, 68)
Possible activities
 Signaling through glycans may lead to malignant B cell survival(48, 49)
 Associated with anti-inflammatory activity of IVIg(13, 74)
 May diminish autoreactivity(25, 71)
Unsolved questions
 Regulation of emergence, starting from largely absent, is unexplored(3)
 Main function(s) still unknown