Exploratory characterization of IgG1/IgG4 glycosylation and monocyte-derived dendritic cell responses in esophageal squamous cell carcinoma.

INTRODUCTION

In previous studies, we identified the unique tumor immunosuppressive function of IgG4. This study aims to further characterize the structure of IgG4 and evaluate its potential effects on monocyte-derived dendritic cells (moDCs).

METHODS

The densities of IgG4 and CD11c in esophageal cancer tissues were detected by immunohistochemistry. IgG1 and IgG4 subclasses were purified from IgG1 and IgG4 subclasses were purified from intravenous immunoglobulin (IVIg) and human serum samples using subclass‑specific affinity chromatography. Human peripheral CD14⁺ monocytes were isolated and induced to differentiate into moDCs in vitro. The migratory and phagocytic capacities of moDCs were then evaluated following stimulation with IgG1 and IgG4.

RESULTS

Immunohistochemical staining revealed that the densities of IgG4⁺ and CD11c⁺ cells were significantly higher in esophageal squamous cell carcinoma (ESCC) tissues than in adjacent normal tissues. Protein electrophoresis, molecular weight analysis, lectin affinity chromatography, and spectrometry demonstrated that native IgG4 exhibits distinct glycosylation profiles compared with IgG1 or commercial myeloma-derived IgG4. IgG4 was predominantly enriched in the ConA⁺ IgG fraction, indicating that it undergoes extensive high-mannose glycosylation. Immunocytochemical staining revealed that peripheral blood-derived monocytes expressed CD68 and CD206, and displayed strong binding affinity for IgG1 but weak affinity for IgG4. In vitro co-culture of moDCs with IgG4 revealed that IgG4 significantly promoted the migration and phagocytic capacity of moDCs relative to IgG1. Furthermore, IgG4 purified from both IVIg and patient serum exerted comparable effects on moDC differentiation.

DISCUSSION: Collectively, these findings suggest that IgG4-associated glycosylation features may be linked to altered phenotypic and functional parameters of moDCs in this exploratory in vitro model. However, the underlying mechanisms, tissue-level relevance, and biological significance require further validation in larger cohorts and more comprehensive functional studies.