TLR7 in B cells promotes renal inflammation and Gd-IgA1 synthesis in IgA nephropathy
Nuoyan Zheng, Kaifeng Xie, Hongjian Ye, Yu Dong, Bing Wang, Ning Luo, Jinjin Fan, Jiaqing Tan, Wei Chen, Xueqing Yu
Nuoyan Zheng, Kaifeng Xie, Hongjian Ye, Yu Dong, Bing Wang, Ning Luo, Jinjin Fan, Jiaqing Tan, Wei Chen, Xueqing Yu
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Research Article Immunology Nephrology

TLR7 in B cells promotes renal inflammation and Gd-IgA1 synthesis in IgA nephropathy

Abstract

TLR7 has been linked to the pathogenesis of glomerulonephritis, but its precise roles are not clear. In this study, we evaluated the roles of TLR7 in IgA nephropathy (IgAN). TLR7 proteins were abundant in CD19+ B cells infiltrated in the kidneys of patients with IgAN. The intensities of both intrarenal TLR7 and CD19 proteins were closely associated with kidney function (estimated glomerular filtration rate [eGFR] and serum creatinine concentration) and renal histopathology (tubular atrophy, leukocyte infiltration, tubulointerstitial fibrosis, and global glomerulosclerosis) in patients with IgAN. Meanwhile, TLR7 mRNA levels were significantly increased in peripheral blood B cells of patients with IgAN. TLR7+CD19+ B cells expressed inflammatory cytokines (IL-6 and IL-12) in kidneys and produced high levels of IgA1 and galactose deficient-IgA1 (Gd-IgA1) in peripheral blood of patients with IgAN. Mechanistically, TLR7 activated B cells to produce high levels of Gd-IgA1 via the TLR7-GALNT2 axis in IgAN. Protein levels of GALNT2 were increased by overexpression of TLR7, while they were reduced by TLR7 knockdown in B cells. GALNT2 overexpression augmented Gd-IgA1 production in B cells derived from patients with IgAN. Taken together, high TLR7 expression in B cells has dual roles in the development and progression of IgAN, by facilitating renal inflammation and Gd-IgA1 antibody synthesis.

Authors

Nuoyan Zheng, Kaifeng Xie, Hongjian Ye, Yu Dong, Bing Wang, Ning Luo, Jinjin Fan, Jiaqing Tan, Wei Chen, Xueqing Yu

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Figure 6

Protein levels of GALNT2 were upregulated in B cells of patients with IgAN after TLR7/8 activation in vitro.

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Protein levels of GALNT2 were upregulated in B cells of patients with Ig...
(A) PBMCs from healthy donors (n = 4–6) were purified and cultured with R848 (5 μg/mL) for 6 days. Cell samples were collected at different time points and sorted into B cells (CD19+) cells and non-B cells (CD19–) by flow cytometry. Cells are subjected to mRNA extraction, cDNA synthesis, and quantitative PCR analysis for target genes using GAPDH as housekeeping gene. (B) Representative Western blot images of protein expression in B cells and non-B cells from R848-activated PBMCs and quantification. PBMCs from donors were prepared and cultured with R848 (5 μg/mL). Cells were collected after 9 days and sorted into B cells (CD19+) and non-B cells (CD19–). Cells are subjected to proteins extraction and Western blot analysis. HC, healthy controls (n = 35, combined as 9 samples); IgAN, patients with IgAN (n = 31, combined as 11 samples); DC, disease controls (MCD/MN) (n = 15, combined as 4 samples). Data were analyzed by 1-way ANOVA with post hoc test. *P < 0.05, **P < 0.01, ***P < 0.001.