Studies On The Relationship Between Tonsillitis And Class Switch Recombination To IgA In IgA Nephropathy

Background:IgA nephropathy is a common disease characterized by predominant IgA deposits in the renal mesangium, up to 43% of patients with IgAN developing end-stage renal failure (ESRF) within 10 years of diagnosis. The pathogenesis of IgAN is not clear until now, Concerning its pathogenesis, several investigators have suggested that IgA deposits are antibodies to viral, bacterial, or dietary antigens. Upper respiratory tract infections and tonsillitis often precede increases in haematuria and proteinuria in IgAN patients, and in some cases tonsillectomy is an efficient treatment for preventing progression of IgAN. These findings suggest that the tonsils in patients with IgAN may act as a source of pathogens responsible for the increase in circulating nephritogenic IgA immune complexes. It's shown that mucosal infections such as tonsillitis are often associated with an acute onset of IgAN. IgAN is therefore an immune complex disease that is caused by a poor mucosal immune response to chronic environmental antigen exposure, and tonsillar mononuclear cells play a important role in the pathogenesis of IgAN. In our previous research, we found that, a-hemolytic streptococci is the most common bacterium in tonsils crypt. So we choose Lipopolysaccharide and a-Hemolytic streptococcus to mimic the immunostimulatory activity to tonsil mononuclear cells. The objective of the present study was to observe IgA production and cell proliferation stimulated with Lipopolysaccharide and a-Hemolytic streptococcus in IgAN. It's proved that AID can be induced in response to some viral and bacterial infections, and then enhance CSR, such as from IgM to IgA. The function of Ig germline transcription is not entirely clear, but some studies show that it is the initial step of CSR. After Germline transcripts produced, it can formate an unstable genomic trimer with Ig, so that the corresponding local gene can keep open, making this part of gene expressed and transcribed. Whether Ig alpha heavy chain of IgAN tonsil B lymphocyte start the remaining Iα-Cαgermline transcripts, together with the expression of AID is related with abnormalities of IgA, is still unclear. Then we observed expression of IgA class switching gene in IgAN tonsillar mononuclear cells before and after stimulated with Lipopolysaccharide andα-Hemolytic streptococcus.Objective:(1) To observe IgA and IgA1 production stimulated with Lipopolysaccharide and a-Hemolytic streptococcus on tonsillar mononuclear cells in IgAN. (2)To observe the expression of IgA class switching gene in Tonsillar mononuclear cells in IgAN before and after stimulated with Lipopolysaccharide and a-Hemolytic streptococcus.Methods:(1) Tonsillar mononuclear cells were isolated by the gradient centrifugation method from 6 cases with IgA nephropathy and 6 cases with chronic tonsillitis. (2) Tonsillar mononuclear cells (1×106 per ml) were cultured for 72h with Lipopolysaccharide or a-Hemolytic streptococcus. (3) IgA and IgA1 production in cultured supernatants were measured in enzyme-linked immunosorbent assay(ELISA). (4) Tonsillar mononuclear cells were isolated by the gradient centrifugation method from IgAN and non-IgAN group. (5)Expression of Iα-Cαgermline transcript, AID(activation induced cytidine deaminase) mRNA were examined by Reverse Transcription Real-time PCR. (6) Expression of AID(activation induced cytidine deaminase) protein were examined by western-blot.Results:(1) Compared to non-IgAN patients,IgA production stimulated with Lipopolysaccharide or a-Hemolytic streptococcus on tonsillar mononuclear cells significantly increased in IgAN patients (P<0.05; P＜0.01). (2) Compared to non-IgAN patients, IgA1 production stimulated with Lipopolysaccharide or Hemolytic streptococcus on tonsillar mononuclear cells significantly increased in IgAN patients (P＜0.05; P＜0.05). (3)IgAl/IgA ratio stimulated with a-Hemolytic streptococcus by Tonsillar mononuclear cells(TMCs) significantly increased in IgAN (P<0.05). (4)Expression of Iα-Cαgermline transcript mRNA in Tonsillar mononuclear cells increased in IgAN patients compared to non-IgAN patients (P<0.05),after stimulated with Lipopolysaccharide or a-Hemolytic streptococcus the difference is significant (P＜0.05; P＜0.05) (5) Expression of AID mRNA in Tonsillar mononuclear cells significantly increased in IgAN patients compared to non-IgAN patients (P<0.05),after stimulated with Lipopolysaccharide or a-Hemolytic streptococcus the difference is significant (P<0.01; P<0.01) (6)Expression of AID protein in Tonsillar mononuclear cells increased in IgAN patients compared to non-IgAN patients, after stimulated with Lipopolysaccharide or a-Hemolytic streptococcus the difference is significant (P<0.01; P<0.01).Conclusion:It reveals that hyper-immune response to antigen and hyperproduction of IgA by Tonsillar mononuclear cells is present in IgAN patients. Expression of Iα-Cαgermline transcript, AID mRNA and protein in Tonsillar mononuclear cells significantly increased in IgAN, it may relate to hyperproduction of IgA in TMCs in IgAN.