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Abstract: PO1810

Novel Model for IgA Nephropathy Using Synthetic Polymeric IgA

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Xie, Xinfang, Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Feinberg Cardiovascular and Renal Research Institute, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
  • Liu, Pan, Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Feinberg Cardiovascular and Renal Research Institute, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
  • Jin, Jing, Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Feinberg Cardiovascular and Renal Research Institute, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States

Group or Team Name

  • 1.Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA; and Feinberg Cardiovascular and Renal Research Institute, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA 2. Department of Nephrology, The First Affiliated Hospital of Medical College, Xi’an Jiaotong University, Xi’an, China
Background

IgA nephropathy (IgAN) is characterized by polymeric IgA deposition in the glomerulus. The mechanism for IgA deposition remains elusive. We constructed a recombinant IgA polymerized by streptavidin to model the initiation and development of IgAN.

Methods

To model IgA complex, we produced recombinant rat and human IgA CH2-CH3 segments. By fusing them with Avi-tag, adding biotin and tetrameric streptavidin to form 4-8-unit multimers. Both dimeric IgA and polymeric IgA constructs were IV injected in rats. Renal deposition of the IgA was detected by immunofluorescence. Polymer IgA was used to stimulate mesangial cells and IL-6 production was measured by ELISA.

Results

Through BirA enzymatic reaction, single biotin was added to the Avi-Tag at the N-terminus of IgA. The total molecular sizes of IgA with and without streptavidin were measured by size-exclusion chromatograph. As expected, uninduced IgA was a standard dimer of 65 kDa, whereas streptavidin-induced IgA formed multimers of 4-8 units, resembling poly-IgA in IgAN. These dimeric and polymeric IgA at 2 mg/kg.BW were injected in 5 week-old Wister rats. 1h, 3 hrs and 24 hrs after injection, the kidney and the liver were harvested for detection of rIgA. Exclusive IgA deposition in the glomerulus mesangial areas was found(Figure). In general, the staining intensity gradually diminished over 24 hrs period. However, rats received daily doses of the induced IgA for 2 and 5 days showed enhanced intensity of IgA deposition. In contrast, the dimeric IgA was not detectable in kidney. Furthermore, EM and PAS staining of the renal sections showed mesangial proliferation. Ex vivo stimulation of human mesangial cells also showed increased levels of IL-6 in the medium.

Conclusion

The findings indicate streptavidin-induced poly-rIgA causes specific renal mesangial deposition and mesangial cells proliferation, which can be used to study the kinetics of mesangial accumulation and clearance of IgA deposition, as a new model for investigating IgAN pathogenesis.