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. 2022 Jan;9(1):e000576.
doi: 10.1136/lupus-2021-000576.

Membrane attack complex (MAC) deposition in renal tubules is associated with interstitial fibrosis and tubular atrophy: a pilot study

Shudan Wang  1   2 , Ming Wu  3 , Luis Chiriboga  3 , Briana Zeck  3 , Beatrice Goilav  4 , Shuwei Wang  5 , Alejandra Londono Jimenez  6   2 , Chaim Putterman  2   7 , Daniel Schwartz  8 , James Pullman  8 , Anna Broder #  6   2 , H Michael Belmont #  9
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Membrane attack complex (MAC) deposition in renal tubules is associated with interstitial fibrosis and tubular atrophy: a pilot study

Shudan Wang et al. Lupus Sci Med. 2022 Jan.

Abstract

Introduction: Treatment failures for lupus nephritis (LN) are high with 10%-30% of patients progressing to end-stage renal disease (ESRD) within 10 years. Interstitial fibrosis/tubular atrophy (IFTA) is a predictor of progression to ESRD. Prior studies suggest that tubulointerstitial injury secondary to proteinuria in LN is mediated by complement activation in the tubules, specifically through the membrane attack complex (MAC). This study aimed to investigate the associations between tubular MAC deposition with IFTA and proteinuria.

Methods: In this cross-sectional study, LN kidney biopsies were assessed for MAC deposition by staining for Complement C9, a component of the MAC. Chromogenic immunohistochemistry was performed on paraffin-embedded human renal biopsy sections using unconjugated, murine anti-human Complement C9 (Hycult Biotech, clone X197). Tubular C9 staining intensity was analysed as present versus absent. IFTA was defined as minimal (<10%), mild (10%-24%), moderate (25%-50%) and severe (>50%).

Results: Renal biopsies from 30 patients with LN were studied. There were 24 (80%) female sex, mean age (SD) was 33 (12) years old and 23 (77%) had pure/mixed proliferative LN. Tubular C9 staining was present in 7 (23%) biopsies. 27 patients had minimal-to-mild IFTA and 3 patients had moderate IFTA. Among the C9 + patients, 3 (43%) had moderate IFTA as compared with none in the C9- group, p=0.009. C9 + patients had higher median (IQR) proteinuria as compared with C9- patients: 6.2 g (3.3-13.1) vs 2.4 g (1.3-4.6), p=0.001 at the time of biopsy. There was no difference in estimated glomerular filtration rate (eGFR) between the C9 + and C9- groups.

Conclusion: This study demonstrated that tubular MAC deposition is associated with higher degree of IFTA and proteinuria, which are predictors of progression to ESRD. These results suggest that tubular MAC deposition may be useful in classification of LN. Understanding the role of complement in tubulointerstitial injury will also identify new avenues for LN treatment.

Keywords: autoimmunity; inflammation; lupus erythematosus; lupus nephritis; systemic.

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Conflict of interest statement

Competing interests: None declared.

Figures

Figure 1
Figure 1
C9 deposition in the tubular basement membrane of a patient with lupus nephritis Class V and moderate interstitial fibrosis/tubular atrophy.
See this image and copyright information in PMC

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