MUC5AC and colitis: B3GALT5 is an enzyme that plays a role in mucin-type O-glycan core extension.21 A recent study showed that the B3GALT5 enzyme protects from DSS colitis by promoting sialylation of MUC2.22 Our mass spectrometry results showed a defect in core-2 elongation of mucin-type O-glycan in naive Il22Ra1IEC mice.