Abstract: TH-PO0272
IgA-IgG-C3 Immune Complexes Stimulate Mesangial Cells in Culture to Increase Cellular Signaling, Protein Uptake, and Production of Extracellular-Matrix Proteins
Session Information
- Glomerular Diseases: Cell Biology
October 22, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Huang, Zhi qiang, University of Alabama at Birmingham, Birminaham, Alabama, United States
- Hall, Stacy D., University of Alabama at Birmingham, Birminaham, Alabama, United States
- Qiu, Shihong, University of Alabama at Birmingham, Birminaham, Alabama, United States
- Shang, Qiao, University of Alabama at Birmingham, Birminaham, Alabama, United States
- Rizk, Dana V., University of Alabama at Birmingham, Birminaham, Alabama, United States
- Julian, Bruce A., University of Alabama at Birmingham, Birminaham, Alabama, United States
- Green, Todd J., University of Alabama at Birmingham, Birminaham, Alabama, United States
- Novak, Jan, University of Alabama at Birmingham, Birminaham, Alabama, United States
Background
Patients with IgA nephropathy (IgAN) have glomerular immune-complex deposits consisting of galactose-deficient IgA1 (Gd-IgA1), IgG autoantibodies, and complement C3. Elevated C3-IgA colocalization is associated with mesangioproliferative injury. These glomerular immune-complexes likely originate from the circulation. Patients with IgAN have unbound circulating IgG autoantibodies; addition of Gd-IgA1 to their sera forms new Gd-IgA1-IgG-C3 immune complexes. However, interaction of Gd-IgA1-containing immune complexes with mesangial cells is not well understood. To address this knowledge gap, we determined biological activities of Gd-IgA1-C3 immune complexes isolated after supplementing sera of IgAN patients with Gd-IgA1.
Methods
IgAN patient serum was supplemented with recombinant polymeric Gd-IgA1. Immune complexes were isolated by size-exclusion chromatography as fractions with Mr ~2 MDa to 0.7 MDa. Quiescent primary human mesangial cells were incubated with these preparations for 15 min and 1, 3, and 24 h, without or with RGD (Arg-Gly-Asp peptide), an inhibitor of integrin α5β1. Uncomplexed Gd-IgA1, IgG, and C3 served as other controls. After incubation, cells were extensively washed and lysed in the presence of protease and phosphatase inhibitors. Cell lysates were analyzed by SDS-PAGE western blotting to determine cell-associated IgA, IgG, and C3 and cellular signaling (phosphorylation of ERK1/2, AKT, and Axl). Cell lysates and culture supernatants were analyzed for fibronectin and laminin.
Results
IgA, IgG, and C3 were detected in the cells incubated with immune complexes for 15 min and 1, 3, and 24 h, but not in control cells. Immune complexes activated ERK1/2 at 15 min; the signal diminished after 3 h. AKT and Axl were activated at 15 min and remained activated at 24 h. RGD reduced cellular uptake of IgA, IgG, and C3 after 24 h and reduced AKT activation. Immune complexes stimulated secretion of fibronectin and laminin at 24 h and RGD reduced the effect by 45% for laminin and by 30% for fibronectin. Uncomplexed Gd-IgA1, IgG, and C3 did not activate AKT but were detected in cell lysates at 1 and 24 h.
Conclusion
IgA-IgG-C3 immune complexes activated mesangial-cell signaling, and increased protein uptake and secretion of fibronectin and laminin. Integrin α5β1 participated in some of these processes.
Funding
- NIDDK Support