Jihye Kim 1 2, Ji Hye Jeong 1 2, Jaehyung Jung 1 2, Hanwool Jeon 3, Seungjoo Lee 3, Joon Seo Lim 4, Heounjeong Go 5, Ji Seon Oh 4, Yong-Gil Kim 1, Chang-Keun Lee 1, Bin Yoo 1, Seokchan Hong 1
Abstract
Objectives: Kidney-infiltrating immune cells can contribute to the pathogenesis of lupus nephritis (LN). We investigated the immunological characteristics of CD11c+ macrophages and their functions associated with the pathogenesis of LN.
Methods: CD11c+ macrophages were examined in the urine samples of patients with LN. Phenotypic markers and pro-inflammatory cytokine expression levels were analysed by flow cytometry. To determine the origin of urinary macrophages, peripheral monocytes were treated with sera from patients with systemic lupus erythematosus (SLE). The pathogenic role of CD11c+ macrophages in tubulointerstitial damage was investigated using SLE sera-treated monocytes and HK-2 cells.
Results: Urinary CD11c+ macrophages expressed pro-inflammatory cytokines, such as IL-6 and IL-1β, and resembled infiltrated monocytes rather than tissue-resident macrophages with respect to surface marker expression. CD11c+ macrophages had high expression levels of the chemokine receptor CXCR3, which were correlated with cognate chemokine IP-10 expression in urinary tubular epithelial cells. When treated with sera from SLE patients, peripheral monocytes acquired the morphological and functional characteristics of urinary CD11c+ macrophages, which was blocked by DNase treatment. Finally, SLE sera-treated monocytes induced fibronectin expression, apoptosis and cell detachment in HK-2 cells via production of IL-6.
Conclusion: CD11c+ macrophages may be involved in the pathogenesis of tubulointerstitial injury in LN.
Keywords: lupus nephritis; macrophage; tubular epithelial cell; tubulointerstitial change; urine.
Fig. 3
Analysis of tubular epithelial cells in the urine of patients with LN
(A) Flow cytometry gating strategy for detection of urinary tubular epithelial cells (TECs; CD10+CD13+CD45−) from LN patients. (B) Correlation between urinary TECs and CD11c+ macrophages (n = 23). (C) Chemokine expressions in urinary TECs (n = 5). (D) Geometric mean fluorescence intensity (gMFI) of CXCR3 in CD11c+HLA-DR+CD14+ cells from the peripheral blood of healthy controls (HC; n = 7), patients without LN (No LN; n = 9) and patients with LN (LN; n = 9). (E) Correlation between CXCR3 in urinary CD11c+ macrophages and IP-10 in urinary TECs (n = 9). (F) Representative immunofluorescence image of CD11c+ (green), IP-10 (red) and 4′,6-diamidino-2-phenylindole (DAPI; blue) in the kidney tissue of patients with proliferative LN. Scale bar: 20 μm. (G) Migration of urinary CD11+ macrophages towards IP-10 in the presence of IgG control, anti-CXCR3 antibody or anti-IP-10 antibody (n = 5). P < 0.05, **P < 0.001.
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