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Abstract: TH-PO545

Characterization of Cell Surface Glycophenotypes of IgA1-Secreting Cells Reveals Distinct Subpopulations and Correlation with Glycosylation of Galactose-Deficient IgA1 in IgA Nephropathy

Session Information

Category: Glomerular Diseases

  • 1401 Glomerular Diseases: From Inflammation to Fibrosis

Authors

  • Person, Taylor, The University of Alabama at Birmingham Department of Microbiology, Birmingham, Alabama, United States
  • Nakazawa, Shigeaki, Osaka Daigaku Daigakuin Igakukei Kenkyuka Igakubu Igaku Senko Kikan Seigyo Gekagaku Hinyoki Kagaku, Suita, Osaka, Japan
  • Rizk, Dana V., The University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States
  • Julian, Bruce A., The University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States
  • Novak, Jan, The University of Alabama at Birmingham Department of Microbiology, Birmingham, Alabama, United States
  • Reily, Colin, The University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States
Background

IgA nephropathy (IgAN) is an autoimmune disease in which the autoantigen, IgA1 with some O-glycans deficient in galactose (Gd-IgA1), is recognized by IgG autoantibodies, and some of the resultant immune complexes deposit in the glomeruli to induce kidney injury. Elevated levels of Gd-IgA1 in the circulation of IgAN patients predict worse outcomes. However, Gd-IgA1 represents only a small portion of total circulatory IgA1. We hypothesize that specific subpopulations of IgA1-secreting cells produce most of the Gd-IgA1. Here, we report that certain cell-surface glycophenotypes correlate with Gd-IgA1 production.

Methods

Immortalized IgA1-producing cells derived from peripheral-blood cells of IgAN patients and healthy controls were live-sorted for IgA+ populations and separated into PNA-low and high subpopulations (PNA lectin is specific for galactose(Gal)-b1,3N-acetylgalactosamine(GalNAc) disaccharide of glycoconjugates). These subpopulations were then incubated for 48 h with a mixture of pro-inflammatory cytokines (IL-4, IL-6, IL-21, CD40L; 50 ng/mL each). Live cells were treated with sialidase (to remove sialic acid that may be attached to Gal, GalNAc, or both), then stained with PNA, HPA (lectin specific for GalNAc), and antibody specific for IgA, followed by flow cytometry analysis. Amounts of IgA1 and Gd-IgA1 secreted into the cell-culture medium were determined by ELISA.

Results

Cell-surface glycosylation of IgA1+ sorted cells was dynamic after expansion of subpopulations. IgA cell-surface expression also changed after the expansion of cells. The frequency of IgA- cells correlated with Gd-IgA1, irrespective of IgA1 sialylation or IgA production (p<0.01; n = 5). Additionally, cell-surface HPA reactivity of PNA-high cells exclusively increased after treatment with sialidase, and negatively correlated with degree of sialylation of secreted Gd-IgA1 (p<0.01; n=5).

Conclusion

We found an inverse correlation of cell-surface GalNAc sialylation with Gd-IgA1 sialylation in PNA-high cells. This observation suggests that some glycosyltransferase pathways are regulated by distinct mechanisms with different impact on cell-surface glycophenotypes and IgA1-glycosylation.

Funding

  • NIDDK Support