Abstract: SA-PO637
Analysis of Galnt14 Null Mice Link O-Glycosylation Defects With Elevated IgA Levels via Altered B-Cell Homing
Session Information
- Glomerular Diseases: IgA and Complement-Mediated GN
November 05, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1302 Glomerular Diseases: Immunology and Inflammation
Authors
- Steers, Nicholas J., Columbia University Irving Medical Center, New York, New York, United States
- Prakash-Polet, Sindhuri, Columbia University Irving Medical Center, New York, New York, United States
- Stevens, Kelsey O., Columbia University Irving Medical Center, New York, New York, United States
- Ng, Anna, Columbia University Irving Medical Center, New York, New York, United States
- Liang, Judy, Columbia University Irving Medical Center, New York, New York, United States
- Novak, Jan, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gharavi, Ali G., Columbia University Irving Medical Center, New York, New York, United States
Background
Defects in O-glycosylation of IgA1 are a characteristic finding in IgA Nephropathy. It is not known if aberrant O-glycosylation can impact other aspects of IgA homeostasis, such as B-cell homing and migration. In humans, up to 20 distinct acetylgalactosaminyltransferases (GALNTs) can initiate O-glycosylation of proteins.
Methods
We studied Galnt14 null mice and compared the circulating and mucosal IgA levels and tissue resident IgA+ B-cells in Galnt14-/- and Galnt14+/+ mice by ELISA and flow cytometry.
Results
GALNT14 is expressed in human and murine lymphoid tissue, including the germinal centers of the spleen and lymph nodes, which are the major sites for B-cell maturation, antibody class switching and proliferation. Serum IgA levels were significantly elevated in the Galnt14-/- mice compared to the Galnt14+/+ mice (1.73 + 0.95 mg/ml, 0.84 + 0.35 mg/ml, P-value < 0.001, respectively). Similarly elevated were mucosal IgA levels in the peritoneal cavity (PC), small intestine (SI), and the colon in Galnt14-/- mice. Flow cytometric analysis of IgA bound to fecal bacteria also demonstrated enhanced binding of IgA to bacteria derived from Galnt14-/- mice compared to the Galnt14+/+ mice (mean fluorescence intensity 5721 + 1028, 4006 + 480, respectively P-value < 0.01). In addition, the percentage of IgA+ B cells in spleen and peritoneal cavity was significantly increased in Galnt14-/- mice. No differences in the percentage IgA+ B-cells in the SI, Peyer’s patches and peripheral blood mononuclear cells were observed between the genotypes, suggesting non-mucosal tissues as the major site of abnormalities in the distribution of IgA-producing cells. Finally, reciprocal adoptive transfer experiments demonstrated that splenic derived B-cells isolated from Galnt14-/- mice had a reduced ability to home to the spleen, regardless of the recipient genotype.
Conclusion
Galnt14-/- mice have a defect in B-cells to home and potentially remain in mucosal and lymph tissues, partially explaining the increased number of IgA+ cells in the spleen and PC, and elevated IgA in the serum of Galnt14-/- mice. We are currently exploring the mechanisms of the alterations observed in B-cell recruitment to mucosal and lymphoid tissue in Galnt14-/- mice.
Funding
- NIDDK Support