IL-17 and IL-23 in lupus nephritis - association to histopathology and response to treatment

Abstract

Background: Recent studies indicate a central role for the IL-23/IL-17 axis in the pathogenesis of lupus nephritis (LN) but the importance in the context of treatment outcome is unknown. We studied various cytokines, including the IL-23/IL-17 axis, in association to histopathology and response to therapy.

Methods: Fifty-two patients with active LN were included. Renal biopsies were performed at baseline and after immunosuppressive treatment. Serum levels of TNF-α, IFN-γ, IL-6, IL-10, IL-17, IL-23 and TGF-β were analysed at both biopsy occasions and in 13 healthy controls. IL-17 expression in renal tissue was assessed by immunohistochemistry. Biopsies were evaluated regarding WHO-classification and renal disease activity was estimated using the BILAG-index. Improvement of 2 grades in renal BILAG was regarded complete response, and 1 grade partial response.

Results: At baseline, all patients had high disease activity (BILAG A/B). Baseline levels of IL-6, IL-10, IL-17, IL-23 (p < 0.001) and IFN-γ (p = 0.03) were increased in patients vs.

Controls: In contrast, TGF-β was lower in patients compared to controls (p < 0.001). Baseline levels of IL-17 were higher in patients with persisting active nephritis (WHO III, IV, V) after treatment, i.e. a poor histological response, vs. WHO I-II (p < 0.03). At follow-up, IL-23 were higher in BILAG-non-responders vs. responders (p < 0.05). Immunostaining of renal tissue revealed IL-17 expression in inflammatory infiltrates.

Conclusions: High baseline IL-17 predicted an unfavourable histopathological response, and BILAG-non-responders had high IL-23, indicating that that a subset of LN-patients has a Th-17 phenotype that may influence response to treatment and could be evaluated as a biomarker for poor therapeutic response.

Figure 1

Baseline levels of IL-17 were higher in patients with an unfavourable histopathological outcome. (a) Baseline levels were significantly higher in patients who had a persisting active nephritis (WHO class III, IV or V) at follow-up, i.e. WHO non-responders, vs.WHO responders (WHO I or II). (b) Baseline levels of IL-17 in patients in relation to histopathology at follow-up. The patient with vasculitis at repeat biopsy was here included in the class III-IV group. The highest levels were seen in patients with a memranous nephritis, WHO class V, at follow-up. Boxes limits show 25^th to 75^th percentile and median values are marked inside the boxes.

Figure 2

Serum levels of IL-17 in patients and controls. Patients with the highest baseline levels had higher levels of IL-23, TNF-α and IFN-γ. (a) Serum levels of IL-17 in patients at baseline and follow-up in patients and levels in controls (medians 97.4, 48.0 and 3.3 pg/ml respectively). The dotted line denotes the upper 25% of IL-17 levels (above 165 pg/ml). The patients with the highest baseline levels of IL-17 (>165) pg/ml had higher levels of IL-23 as shown in (b), TNF-α (c) and IFN-γ (d) vs. those with IL-17 levels < 165. Boxes limits show 25^th to 75^th percentile and median values are marked inside the boxes.

Figure 3

Patients with persisting high levels of IL-17 at follow-up had higher levels of TNF-α and IFN-γ. Patients with persisting high levels of IL-17 (>165 pg/ml) had significantly higer levels of TNF-α (a) and IFN-γ (b) vs those with IL-17 < 165 pg/ml. Boxes limits show 25^th to 75^th percentile and median values are marked inside the boxes.

Figure 4

Follow-up levels of IL-23 were higher in patients with an unfavourable BILAG response. (a) Serum levels of IL-23 in patients at baseline and follow-up in patients and levels in controls (medians 5.5, 3.3 and 0.7 pg/ml respectively). (b) Levels of of IL-23 in all patients were significantly higher in BILAG non-responder (NR) patients vs. partial- (PR) and complete responders (CR), this was most pronounced in the group of patients with WHO class V at follow-up as shown in (c). Boxes limits show 25^th to 75^th percentile and median values are marked inside the boxes.

Figure 5

Immunostaining of IL-17 in renal tissue. The figure demonstrates a kidney biopsy from a patient with lupus nephritis WHO class V. Representative micrographs displaying (A) an inflammatory infiltrate with T cells as demonstrated by a positive CD3-staining and in (B) the same infiltrate from a consecutive section stained with irrelevant isotype control antibody. In (C), IL-17 staining is demonstrated, predominantly found in the inflammatory infiltrate shown in A, and (D) demonstrates staining with the corresponding isotype control antibody. Original magnifications: 12.5×.