title: Expression of IgA class switching gene in tonsillar mononuclear cells in patients with IgA nephropathy.
abstract: OBJECTIVE
  There are many reports suggesting a relationship between the tonsillar autoimmune response and the pathogenesis of IgA nephropathy (IgAN). Hyperproduction of IgA and IgA1 in tonsils could be caused by activation of the Ig class switching recombination (CSR). αGLT (germline transcripts) plays a critical role in the initiation of switching from Cμ to Cα, resulting in production of IgA. Activation-induced cytidine deaminase (AID) is a molecule essential for CSR and Ig gene conversion. The aim of this study was to investigate IgA and IgA1 levels in the supernatant of tonsillar mononuclear cells (TMCs) and the expression of Iα-Cα germline transcript and AID in TMCs stimulated with lipopolysaccharide or hemolytic streptococcus in IgAN patients and chronic tonsillitis patients.
  
  
  METHODS
  27 IgAN patients were admitted into our hospital from Jan. 2009 to Feb. 2010. Another 27 patients with chronic tonsillitis but without renal disease were selected as the control group. Tonsillar lymphocytes were isolated by density gradient centrifugation using Lymphocyte Separation Medium. The amount of IgA or IgA1 secreted in the culture supernatants was determined by specific enzyme-linked immunosorbent assay. Expressions of Iα-Cα germline transcript and AID mRNA were examined by reverse transcription real-time PCR. The AID protein was determined by Western blotting.
  
  
  RESULTS
  The production of IgA and IgA1 protein, especially the ratio of IgA1/IgA in TMCs stimulated with or without 10 μg/ml of lipopolysaccharide or 1 × 10(8 )cfu/ml of hemolytic streptococcus, were significantly increased in the IgAN group compared with that in the non-IgAN group (P < 0.05), and the IgA and IgA1 levels in TMCs stimulated with 10 μg/ml of lipopolysaccharide or 1 × 10(8 )cfu/ml of hemolytic streptococcus were markedly increased in patients with IgAN compared with the control group (P < 0.05).The expressions of Iα-Cα and AID mRNA were significantly upregulated in TMCs stimulated with 10 μg/ml of lipopolysaccharide or 1 × 10(8 )cfu/ml of hemolytic streptococcus in patients with IgAN compared with control group (P < 0.05). The expression of AID protein in TMCs stimulated with or without 10 μg/ml of lipopolysaccharide or 1 × 10(8 )cfu/ml of hemolytic streptococcus was significantly increased in the IgAN group compared with that in the non-IgAN group (P < 0.05). The expression of AID protein in TMCs stimulated with 10 μg/ml of lipopolysaccharide or 1 × 10(8) cfu/ml of hemolytic streptococcus was significantly increased in patients with IgAN compared with the control group (P < 0.05, P < 0.01).
  
  
  CONCLUSIONS
  Lipopolysaccharide or hemolytic streptococcus can induce the production of IgA and IgA1 and the expression of AID and Iα-Cα in TMCs from patients with IgAN. Our results indicate that the TMCs from patients with IgAN are capable of producing high levels of IgA and IgA1 when stimulated with lipopolysaccharide or hemolytic streptococcus, which may be due to the increased expression of AID and Iα-Cα.
authors: Nephrology Department, Renal Research Institute, Hunan Key Lab of Kidney Disease and Blood Purification, 2nd Xiangya Hospital, Central South University, Renmin Road 139#, Changsha, 410011, Hunan, People's Republic of China.
authors: Hong
authors: H
authors: Liu
authors: Youming
authors: Y
authors: Peng
authors: Fuyou
authors: F
authors: Liu
authors: Weiwei
authors: W
authors: Xiao
authors: Yu
authors: Y
authors: Zhang
authors: Weiwei
authors: W
authors: Li
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