Interstitial Inflammation in the ISN/RPS 2018 Classification of Lupus Nephritis Predicts Renal Outcomes and is Associated With Bcl-2 Expression

OBJECTIVE: To investigate the histopathological characteristics of patients with lupus nephritis in the 2018 revised International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification and assess the prognostic factors. METHODS: This study enrolled 92 patients with lupus nephritis, who had conventional treatment and renal biopsy. Each renal tissue was evaluated according to 2018 ISN/RPS classification, and quantified apoptotic regulator protein, the B-cell lymphoma-2 protein (Bcl-2), expressions in selected lymphocyte subsets were measured using novel computational approaches using multicolor confocal images. Histopathological characteristics and prognostic factors of end-stage renal disease (ESRD) and chronic kidney disease (CKD) were compared. Follow-up data were obtained, and survival analysis was conducted. RESULTS: During follow-up period (average 74.3 months), 16 and 18 patients progressed ESRD and CKD, respectively. Multivariable analysis of age, sex, disease activity and pathological features in ISN/RPS demonstrated the extent of interstitial inflammation (grade 0~3) was significantly associated with both ESRD and CKD. When interstitial inflammation was divided into mild (grade 0, 1) and severe (grade 2, 3), Cox regression analysis showed that patients with severe interstitial inflammation were significantly increased risk of both ESRD and CKD (hazard ratio 4.67 and 3.8, respectively). Bcl-2 expression in CD4+ and CD20 cells was significantly higher in the severe interstitial inflammation group compared to in mild interstitial inflammation patients (p=0.006 and 0.010, respectively). CONCLUSION: The extent of interstitial inflammation can predict clinical renal outcomes. Significantly elevated Bcl-2 expression in both CD4+ and CD20 cells was found in severe interstitial inflammation compared with mild interstitial inflammation.