Assessing serum IgG4 glycosylation profiles of IgG4-related disease using lectin microarray.

OBJECTIVES IgG4 related disease (IgG4-RD) is a multiorgan fibroinflammatory disorder. Lectin microarray is a high-throughput glycosylation analysis technology. The aim of our study was to investigate glycosylation profiling of serum IgG4 from IgG4-RD patients and controls. METHODS A large cohort of 167 IgG4-RD patients, 130 disease controls (DCs) and 86 healthy controls (HCs) were included in the current study. The glycan level of serum IgG4 of all participants was determined by lectin microarray. A verification assay of lectin microarray and lectin blot were used to clarify the relationship between the serum IgG4 and purified IgG4 glycosylation. RESULTS The results revealed that the glycan level of mannose (binding MNA-M, VVA mannose, ConA) was significantly increased and that the glycan level of fucose (binding LTL), GlcNAc (binding DSL), GalNAc (binding HPA) was significantly decreased in IgG4-RD patients compared to DCs and HCs. We further found that the glycan level of GlcNAc was positively correlated with that of complement 3 (C3), and that the reduced level of GlcNAc was associated with damage to multiple organs. In addition, the mannose level (binding MNA-M and VVA mannose) was negatively correlated with C3 and complement 4 (C4) levels. CONCLUSIONS Serum IgG4 of IgG4-RD patients exhibits different glycosylation levels. This study demonstrated that there is important clinical value in identifying aberrant GlcNAc levels as a potential diagnostic index for multi-organ involvement. Furthermore, the mannose level of serum IgG4 may reflect the degree of inflammation of IgG4-RD.