Lupus nephritis correlates with B cell interferon-β, anti-Smith, and anti-DNA: a retrospective study

Abstract

Background: In systemic lupus erythematosus (SLE), detection of interferon-β (IFNβ) in B cells was found to be most prominent in patients with high anti-Smith (Sm) and renal disease, but a mechanistic connection was not clear. The objective of the present study is to determine the association of IFNβ in peripheral blood naïve B cells with the histopathological features of lupus nephritis (LN).

Methods: The percentage of IFNβ⁺ cells in IgD⁺CD27^- naïve CD19⁺ B cells (B cell IFNβ) among peripheral blood mononuclear cells (PBMCs) from 80 SLE patients were analyzed using flow cytometry. Serological and clinical data were collected. The correlations of B cell IFNβ with LN classification and with histopathological findings (light, electron, and immunofluorescence [IF] microscopic analyses for deposition of IgM, IgG, IgA, C1q, and C3) were determined in 23 available biopsy specimens.

Results: B cell IFNβ is positively associated with anti-Sm (p = 0.001), anti-DNA (p = 0.013), and LN (p < 0.001) but was negatively associated with oral/nasal ulcer (p = 0.003) and photosensitivity (p = 0.045). B cell IFNβ positively correlated with immune complex (IC) deposit in the glomerular basement membrane (GBM) (p = 0.002) but not in the mesangial (p = 0.107) or tubular region (p = 0.313). Patients with high B cell IFNβ had statistically increased development of the proliferative LN (Classes III, IV and/or V), compared to patients with low B cell IFNβ (p < 0.0001). Histopathological features positively associated with increased B cell IFNβ included active glomerular lesions as determined by fibrocellular crescents (p = 0.023), chronic glomerular lesions indicated by segmental sclerosis (p = 0.033), and a membranous pattern of renal damage indicated by spike/holes (p = 0.015).

Conclusion: B cell IFNβ correlates with history of severe LN, glomerular basement membrane (GBM) IC deposition, and anatomical features of both active and chronic glomerular lesions.

Keywords: Autoantibodies; B cell interferon beta; Lupus nephritis; Systemic lupus erythematosus.

Fig. 1

Flow cytometry analysis of IFNβ⁺ naïve B cells. A–C Flow cytometry plots showing the sequential gating of IFNβ in naïve B cells based on the indicated cell surface markers in a representative SLE patient with high B cell IFNβ (A), a representative SLE patient with low B cell IFNβ (B), and a representative healthy control donor (C). D Bar graph showing the percentages of IFNβ⁺ naïve B cells in SLE patients and healthy controls (PB, plasmablasts/plasma cells, HC; healthy control) (data are mean ± SD; unpaired t-test)

Fig. 2

Association of clinical and laboratory parameters with B cell IFNβ in SLE patients. Eighty SLE patients were analyzed for B cell IFNβ and other clinical and laboratory characteristics. A Principal component (PC) analysis of 18 parameters and B cell IFNβ. The clinical parameters indicated near the position of the PC analysis plot and the p value of each parameter as being associated with B cell IFNβ is shown in the parenthesis. Variants shown in red exhibit significant positive correlation with B cell IFNβ. Variants shown in blue exhibit significant negative correlation with B cell IFNβ. B Linear regression analysis of anti-Smith (top) and anti-DNA (bottom) with B cell IFNβ. Anti-Sm was shown as U/mL. Anti-DNA was shown as OD₄₅₀. R², p value, and number of subjects (n) are indicated. C–E Bar graph showing the percentages of IFNβ⁺ naïve B cells in SLE patients with (positive) or without (negative) LN (C), photosensitivity (D), and oral/nasal ulcer (E) (mean ± SD; unpaired t-test with the p value shown in each panel)

Fig. 3

Association of B cell IFNβ with LN-related laboratory parameters and SLEDAI. A Complement C3 (mg/dL) and C4 (mg/dL) at the time of enrollment were plotted against the percentages of IFNβ⁺ naïve B cells. B Urinary protein/creatinine ratio at the time of enrollment was plotted against the percentages of IFNβ⁺ naïve B cells. C SLEDAI score was plotted against the percentages of IFNβ⁺ naïve B cells. D Anti-Sm at any time was plotted against anti-Sm at the time of enrollment. E Anti-Sm (unit) at any time was plotted against the percentages of IFNβ⁺ naïve B cells (linear regression analysis. The R², p value, and the number of subjects are shown on the plot)

Fig. 4

Association of B cell IFNβ with the location of immune complexes in renal biopsy. Renal biopsies were obtained from 23 available specimens. The immune complexes were scored based on the presence each indicated type in the glomerular basement membrane (A), mesangium (B), renal tubular (C), and arterioles/arteries (D) using a 0 to 4 scoring range: 0, absent, 1 rare, 2 low abundance, 3 moderate abundance, and 4 high abundance. LN patients were divided into two groups based on the levels of B cell IFNβ either below the mean (IFNβ low, n = 10) or above the mean (IFNβ high, n = 13) (data are mean ± SEM; 2-way ANOVA test on the effects of B cell IFNβ and IC type in each region)

Fig. 5

Quantitative analysis of renal biopsy features with B cell IFNβ. A The distribution of LN classification in patients with low (lower 50%) versus high (upper 50%) B cell IFNβ. The p value (chi-squared test) is shown above the plot (n = 33). B–F The histologic features were analyzed using renal biopsy specimens available from 23 SLE patients. For each histologic feature, the individual percentage of IFNβ⁺ naïve B cells was plotted for each subject and indicated by the data-point on the graph, ranging from 0 to 100%. Histologic features associated with active glomerular lesions (B), chronic glomerular lesions (C), activity index and chronicity index (high: above the mean; low: below the mean) (D), membranous patterns of spike/holes (E), and tubulointerstitial lesions (F). The p value for each comparison is indicated as the number above the groups. Statistically significant differences are indicated in red. (data are mean ± SD; two-tailed Mann-Whitney test)