Study on the binding capacity of IgA1 from patients with IgA nephropathy to human mesangial cells |
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Authors: | WANG Yue ZHAO Ming-hui ZHANG You-kang WANG Hai-yan |
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Institution: | Renal Division. the First Hospital & Institute of Nephrology, Peking University, Beijing 100034, China |
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Abstract: | AIM: To examine and compare the ability of serum IgA 1, from both the patients with IgA nephropathy(IgAN) and the healthy control, to bind to human mesangial cells(HMC). METHODS: Serum IgA was isolated with jacalin column, heated to aggregated form(IgA1) and labeled with 125I]. Binding capacity of IgA1 to primary HMC was evaluated by radioligant binding assay, specificity of binding was determined by competitive inhibition, and relative affinities was compared by cross competitive inhibition. RESULTS: Both IgA1 from normal control and patients with IgAN bound to MC in a dose-dependent, saturatable manner, but the binding of IgA1 from patients was saturated at approximately 200 pmol while that from healthy was at 400 pmol. The Scatchard analysis revealed a Kd of(8.9±2.1)×10-8 mol/L for patient' s IgA1 versus(4.3±1.2)×10-7mol/L for normal IgA1(P<0.05). Competition inhibition showed that both serum albumin and IgG could not block the binding of IgA1 to HMC while mIgA 1 could partially block that. Cross competition inhibition demonstrated that patient' s IgA1 blocked normal IgA1 binding significantly(P<0.01), however, normal IgA1 was unable to inhibit the binding of patient' s IgA1. CONCLUSIONS: ①There are IgA binding proteins or receptors on mesangial cells. ②IgA1 from patients with IgAN has a higher binding capacity than that from healthy. |
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Keywords: | Glomerulonephritis IGA Carrier proteins |
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