Affinity Purification Coupled to Stable Isotope Dilution LC-MS/MS Analysis to Discover IgG4 Glycosylation Profiles for Autoimmune Pancreatitis

Abstract

Type 1 autoimmune pancreatitis (AIP) is categorized as an IgG4-related disease (IgG4-RD), where a high concentration of plasma IgG4 is one of the common biomarkers among patients. IgG Fc-glycosylation has been reported to be potential biosignatures for diseases. However, human IgG3 and IgG4 Fc-glycopeptides from populations in Asia were found to be isobaric ions when using LC-MS/MS as an analytical tool. In this study, an analytical workflow that coupled affinity purification and stable isotope dilution LC-MS/MS was developed to dissect IgG4 glycosylation profiles for autoimmune pancreatitis. Comparing the IgG4 and glycosylation profiles among healthy controls, patients with pancreatic ductal adenocarcinoma (PDAC), and AIP, the IgG4 glycosylations from the AIP group were found to have more digalactosylation (compared to PDAC) and less monogalactosylation (compared to HC). In addition, higher fucosylation and sialylation profiles were also discovered for the AIP group. The workflow is efficient and selective for IgG4 glycopeptides, and can be used for clinical biosignature discovery.

Editorial: Immune dysfunction in acute pancreatitis: from bench to bedside research

“…N-glycans attach to the conserved asparagine 297 in the fragment crystallizable (Fc) portion of this molecule (altering IgG conformation and interactions with various receptors) and act as a switch between pro- and anti-inflammatory IgG functionality ( 20 ). IgG N-glycosylation affects physiology and an altered profile of IgG N-glycans contributes to disease progression and has been implicated in autoimmune pancreatitis, type 2 diabetes and cardiovascular disease ( 21 , 22 ). The study by Chen et al.…”