Anti-Galectin-3 and Anti-Cytokine Antibodies in IgG4-Related Disease

Abstract

IgG4-Related Disease (IgG4-RD) is a chronic, immune-mediated disease that typically manifests as tumor-like enlargement of various organs. Prior work suggests a role for plasmablasts and CD4+ cytotoxic T lymphocytes (CD4+ CTLs), both of which are found in the tissue at high numbers, decline in response to therapy and demonstrate clonally-restricted antigen receptors. However, the antigens that drive the clonal proliferation of these B and T cell types remain largely unknown. Studies employing Next Generation Sequencing, single cell cloning and quantitative mass spectrometry have identified galectin-3 as a dominant auto-antigen in IgG4-RD. Here, we have expanded this work to examine the frequency of anti-galectin-3 auto-antibodies and quantify plasma galectin-3 levels in a large, clinically diverse cohort of IgG4-RD patients. Anti-galectin-3 auto-antibodies were detected in 6/121 (5%) of the cohort. Five of these 6 subjects were also found to have anti-galectin-3 antibodies of the IgG4 subclass. 15.5% of the subjects were found to have elevated galectin-3 levels in the plasma. Of those subjects with increased plasma galectin-3, 14.3% had concurrent anti-galectin-3 auto-antibodies compared with only 4.7% of those subjects with normal galectin-3 levels. We have also studied the presence of anti-galectin-3 auto-antibodies in 3 of the subjects longitudinally to correlate with disease activity and treatment status. Finally, we have analyzed laboratory parameters and organ manifestations for correlation with elevated galectin-3 levels. As an alternative antigen discovery approach to that mentioned above, a cytokine microarray has been used to test the plasma from a limited cohort of 13 IgG4-RD subjects. Of the culprit “hits,” anti-IL-6, anti-CXCL1 and anti-CCL23 antibodies were confirmed by ELISA in the same cohort. Additionally, a monoclonal antibody from one of these subjects was found to bind CCL23. The current study aims to validate the presence of anti-IL-6 antibodies, anti-CXCL1 antibodies and anti-CCL23 antibodies in our much larger cohort of 130 IgG4-RD subjects.