Background/Purpose: Lupus nephritis (LN) is one of the most severe manifestations of systemic lupus erythematosus (SLE), which is characterized by abnormal B-cell activation and their subsequent differentiation into autoreactive plasma blasts/cells. The heterogeneity of autoreactive B cell subsets and their contribution to the pathogenesis of LN are not well elucidated.

Methods: Thirty-five SLE patients, including twenty-eight with positive anti-dsDNA antibodies (80%), and fifteen healthy controls were recruited in this study. Data are represented as median and interquartile range (IQR). To identify DNA-reactive B cells, a surrogate peptide (DWEYSVWLSN) that serves as dsDNA mimotope was used, as previously shown (Jacobi, Annett M et al. 2009 and Wangriatisak, Kittikorn et al. 2021). The phenotype of peripheral B cell subsets (SLE, n = 37 from 35 patients and HCs, n = 15) and DNA-reactive B cells (SLE, n = 10 and HCs, n = 6) was analyzed by spectral flow cytometry. Correlations between different B-cell subsets and Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score, clinical manifestations, and laboratory parameters were assessed.

Results: In SLE patients, the median SLEDAI-2K score was 9 (4-17), median age and disease duration were 34 (28-46) and 9 (1.5-13.0), respectively. Twenty-one patients presented with lupus nephritis (LN), with proliferative (class III, n = 3 and class IV, n = 4), membranous (class V, n = 7) and mixed histological patterns (class III & V, n = 5 and class IV & V, n = 2). Phenotypic analyses showed an expansion of circulating activated naïve (aNAV: CD11c⁺CD21^–CD27^–IgD⁺, p < 0.01), double negative 2 B cells (DN2: CD11c⁺CD21^–CD27^–IgD^–, p < 0.05) and plasmablasts (PB: CD27^hiCD38^hi, p < 0.05) in LN patients, especially in class V, compared to non-LN and age-matched HCs. Intriguingly, an upregulation of CD71, as well as a downregulation of CD95, was observed on both DN2 and PB from patients with LN. Further analysis showed that expansion of DNA-reactive B cells was observed in LN patients (median (IQR): 0.13% (0.095-0.160)) compared with non-LN patients (median (IQR): 0.056% (0.042-0.070), p < 0.05). Surprisingly, the majority of these autoreactive cells were mostly represented by an activated naïve phenotype (CD11c⁺CXCD5^–CD21^–), which was more frequent in patients with LN. The percentage of aNAV B cells were positively associated with DN2 (r = 0.567, p = 0.0003) and PB (r = 0.498, p = 0.002), especially in patients with LN. These expanded aNAV, DN2 and PB showed a significant positive correlation with the SLEDAI-2K index, and were inversely correlated with C3 and C4 levels in LN patients. Furthermore, DN2 and aNAV B cells were expanded in anti-dsDNA positive patients, while a lower frequency of such cells was found in anti-Smith positive patients.

Conclusion: Our data show that aNAV B cells display autoreactivity to dsDNA. The cooperation between these cells and DN2 and PB might be involved in the generation of anti-dsDNA antibody in LN which proceed of these B cell responses might via the extrafollicular pathway.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/activated-naive-dna-reactive-b-cells-in-lupus-nephritis-patients-are-increased-and-associated-with-disease-activity/