Abstract: FR-PO809
Complement C3 Contributes to the Pathogenicity of Galactose-Deficient IgA1-Containing Immune Complexes in IgA Nephropathy
Session Information
- Glomerular Diseases: Inflammation and Immunology
October 25, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Hall, Stacy D., The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gurganus, Graham, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Huang, Zhi qiang, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Knoppova, Barbora, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Qiu, Shihong, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- King, Rodney G., The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Nakazawa, Shigeaki, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Maillard, Nicolas, Hospital and University Jean Monnet of Saint-Etienne, Saint-Etienne, France
- Moldoveanu, Zina, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Rizk, Dana V., The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Julian, Bruce A., The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Renfrow, Matthew B., The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Green, Todd J., The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Novak, Jan, The University of Alabama at Birmingham, Birmingham, Alabama, United States
Background
IgA nephropathy (IgAN) is an autoimmune kidney disease wherein circulating immune complexes (IC) contain IgA1 with some O-glycans deficient in galactose (galactose-deficient IgA1; Gd-IgA1) bound by IgG autoantibodies specific for Gd-IgA1. Additional serum components, such as complement proteins, can be also associated with these IC. Some of these Gd-IgA1-containing IC deposit in the glomeruli and induce kidney injury. In this study, we assessed the role of complement C3 in the pathogenicity of Gd-IgA1-IgG IC.
Methods
IC from native or IgA1-depleted sera of patients with IgAN were isolated by size-exclusion chromatography. Engineered IC were formed using recombinant polymeric Gd-IgA1 and recombinant IgG autoantibodies specific for Gd-IgA1 in C3-depleted or C3-repleted serum and isolated by size-exclusion chromatography. Biological activity of the isolated IC or engineered IC was determined based on their capacity to induce cellular proliferation of cultured primary human mesangial cells. IgA, Gd-IgA1, and IgA-IgG and IgA-C3 complexes were determined by ELISA. SDS-PAGE immunoblotting under non-reducing conditions was used to determine covalent association of C3 with IgA or IgG. Reducing conditions were used to determine C3 processing, i.e., presence of alpha-chain or its fragments indicative of C3, C3b, and iC3b, respectively.
Results
IC >700 kDa from IgAN sera increased cellular proliferation of quiescent mesangial cells by 2-4-fold. These IC contained IgA, IgG, and C3; C3 was covalently associated with IgA and IgG. C3 molecular forms included C3, C3b, and iC3b. Removal of IgA1 from sera removed these stimulatory IC; the resultant preparations were devoid of IgA, IgG, and C3. To confirm the role of C3, we used engineered IC formed in C3-depleted or repleted serum. C3 was required for formation of large-molecular-mass engineered IC that stimulated mesangial cells to proliferate. Moreover, IgA and IgG formed covalent complexes with C3 in C3-repleted serum; these engineered IC contained C3, C3b, and iC3b.
Conclusion
In summary, C3 has a central role in the formation of Gd-IgA1-containing IC with a nephritogenic capacity for IgAN.
Funding
- NIDDK Support