Integrating longitudinal serum IL-17 and IL-23 follow-up, along with autoantibodies variation, contributes to predict bullous pemphigoid outcome

Abstract

Bullous pemphigoid (BP) is an inflammatory autoimmune bullous disease involving cytokines and proteases in the process of blister formation. Recently, IL-17 and IL-23 were evidenced in lesional skin and serum of BP patients at time of diagnosis, but their involvement in disease outcome has still not been investigated yet. We then analysed IL-17 and IL-23 serum levels during the first months of follow-up upon treatment. Compared with age- and sex- matched controls, high levels of IL-23 were observed at baseline in BP patients serum (P < 0.01), while IL-17 levels was not. However, some BP patients expressed high IL-17 serum level, independently of disease severity. In these patients, those with ongoing remission reduced IL-17 concentration upon treatment (P < 0.001), whereas IL-17 level remained elevated in patients who relapsed. Meanwhile, IL-23 serum levels increased during the first month of treatment in BP patients who later relapsed (P < 0.01) and MMP-9 serum level was not controlled. Accordingly, we found that both IL-17 and IL-23 increased MMP-9 secretion from leukocytes in-vitro. Then, we showed that elevated IL-17/IL-23 serum concentrations helped to discriminate BP patients who later relapsed. Such uncontrolled inflammatory response raises the question whether these molecules could become biological target for BP patients resistant to steroid treatment.

Figures

Figure 1. Variations of IL-17 and IL-23 levels in BP patients compared to healthy controls.

Serum concentrations of IL-17 (a) and IL-23 (b) were measured by ELISA in BP patients at time of diagnosis and in healthy controls. (**P  < 0.01).

Figure 2. Variations of IL-17 and IL-23 concentration in BP serum from baseline until day 150.

Serum concentrations of IL-17 (a) and IL-23 (b) were measured by ELISA at time of diagnosis, 60 days and 150 days after the inclusion of BP patients. (**P  < 0.01) Abbreviations: D0, day 0; D60, day 60; D150, day 150.

Figure 3. Variations of IL-17 concentrations in BP serum from baseline until day 60 according to later BP relapse.

Serum concentrations of IL-17 were measured by ELISA at time of diagnosis and at day 60 in patients who were in remission (a) and patients who further relapsed (b). The subgroup of patients who expressed IL-17 at diagnosis (a) was analysed and divided into 2 subgroups: the first one for which IL-17 concentration was higher than 100 pg/ml at diagnosis (c) and the second one for which IL-17 concentration was higher than 0 but lower than 100 pg/ml (d). (**P < 0.01; ***P < 0.001)

Figure 4. Variations of IL-23 concentrations in BP serum from baseline until day 60 according to later BP relapse.

Serum concentrations of IL-23 were measured by ELISA at time of diagnosis and at day 60 in patients in remission (a) and patients who later relapsed (b). The group of patients who further relapsed was divided into 2 subgroups according to IL-23 concentrations at diagnosis: in serum in which IL-23 was undetectable at time of diagnosis (c), and in serum in which IL-23 was detectable at diagnosis (d). (**P < 0.01; ***P < 0.001)

Figure 5. Distribution of IL-17 and IL-23 expression in BP populations.

Venn diagram showing the number of patients that express IL-17 alone, IL-23 alone and both IL-17 and IL-23 at diagnosis in global BP population (a), and in the population of BP patients who were controlled under therapy (b) and who further relapsed (c).

Figure 6. MMP-9 secretion is regulated by IL-17 and IL-23 and varied along the treatment.

Lymphocytes, monocytes and polymorphonuclear cells (PMN) were isolated from 5 healthy controls and stimulated with IL-17 (200 pg/ml), IL-23 (100 pg/ml) or both cytokines for 20 hours (mononuclear cells) or 1 hour (PMN). MMP-9 secretion was analysed by gel zymography. One representative zymogram was shown for each type of cells and quantification of zymogram was performed using ImageJ software (a). MMP-9 secretion was analysed by gel zymography in BP patients in remission or with relapse at diagnosis and at day 60 (b).