Abstract: TH-PO037

Racial Comparison of IgA1 Hinge-Region O-Glycoforms by High-Resolution Mass Spectrometry

Session Information

Category: Glomerular

  • 1001 Glomerular: Basic/Experimental Immunology and Inflammation

Authors

  • Ohyama, Yukako, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Hasegawa, Midori, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Novak, Jan, University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Hiki, Yoshiyuki, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Yuzawa, Yukio, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Takahashi, Kazuo, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Matsushita, Shoko, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Yamaguchi, Hisateru, Fujita Health University, Toyoake, Aichi, Japan
  • Nakajima, Kazuki, Fujita health university, Toyoake, Aichi, Japan
  • Mizuno, Tomohiro, Meijo university, Nagoya, Aichi, Japan
  • Hayashi, Hiroki, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Koide, Shigehisa, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
  • Inaguma, Daijo, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
Background

Prevalence of IgAN varies among racial groups, being more common in Asians, moderately prevalent in Europeans, and rare in Africans. IgA1 with galactose (Gal)-deficient hinge-region (HR) O-glycans (Gd-IgA1) plays a key role in the pathogenesis of IgAN. Relationship of serum Gd-IgA1 levels and race-specific susceptibility to IgAN is not known. To understand race-specific IgA1 O-glycan heterogeneity, we determined serum Gd-IgA1 levels in healthy volunteers of different races and profiled the corresponding IgA1 O-glycoforms.

Methods

Serum Gd-IgA1 was determined by ELISA using novel monoclonal antibody specific for Gd-IgA1 (35A12, Tomiyama Laboratory Co. Ltd., Tokyo, Japan). Human serum IgA1 was purified by affinity chromatography. After neuraminidase treatment and trypsin digestion, IgA1 O-glycan HR heterogeneity was analyzed by liquid chromatography-high-resolution mass spectrometry (LC-MS). To increase the throughput of the analysis, we developed an in-house automated program, Glycan Analyzer. The attachment site(s) of the Gal-deficient O-glycan chain(s) were identified by electron-transfer dissociation (ETD) tandem MS after selective removal of galactosylated O-glycans.

Results

Serum Gd-IgA1 levels were determined in 50 healthy subjects recruited from White, Black, Hispanic, Asian, and Japanese. Gd-IgA1 levels were lower in Asians, including Japanese subjects. His208-Arg245 HR was present in 12 different glycoforms with 3-6 O-glycans. Approximately 58% of HR O-glycoforms contained one to three Gal-deficient O-glycans in IgA1 samples from the subjects of all races. ETD tandem MS revealed that Gal-deficient O-glycans were consistently attached at specific sites.

Conclusion

Despite high susceptibility to IgAN in Asians, Gd-IgA1 levels in Asians were lower compared to other races. Furthermore, HR O-glycoforms with Gal-deficient O-glycans were found also in healthy subjects. Detailed analysis of IgA1 HR O-glycoforms, including sites of glycan attachment, will be important for investigation of pathogenic form(s) of IgA1 in IgAN.

Funding

  • Government Support - Non-U.S.