2.10 Statistical analysis
The Prism version 6 software (GraphPad Software, San Diego, CA, USA) was used for statistical analysis. Data were expressed as the mean ± standard error of the mean (SEM) or standard deviation (SD). All P values were calculated using the Student’s t -test or one-way analysis of variance (ANOVA). Statistical significance was set at P < 0.05.
3. Results
3.1 Expression of IL-35 was significantly increased in patie nts with psoriasis
To investigate the involvement of IL-35 in skin diseases, we first examined IL35 expression in the serum of healthy controls and patients with psoriasis. We recruited patients (n = 53) and age/sex-matched healthy donors (n = 20); the demographics are summarised in Table 1. Using ELISA, we found that the levels of IL-35 were significantly elevated in the serum from patients with psoriasis compared with those in healthy controls (Fig. 1A, p = 0.0089). Moreover, we observed that as the symptoms of psoriasis worsened (increased PASI score), the expression of IL-35 was increased. More specifically, the expression of IL-35 in specimens with a PASI score greater than or equal to 3 points was significantly higher than that in specimens with a PASI score less than 3 points (Fig. 1A). We also found increased populations of CD4+EBI3+p35+ and CD19+EBI3+p35+cells in the peripheral blood of patients with psoriasis via flow cytometry (Fig. 1B-D). We demonstrated that IL-35 secreted by both T and B lymphocytes was significantly increased (p < 0.01 and p < 0.05, respectively). Moreover, immunofluorescence staining results showed that the expression of IL-35 in the skin tissue of patients with psoriasis increased significantly (Fig. 1E).
3.2 M-MDSCs were significantly expanded in patients with psoriasis
We examined whether the number of M-MDSCs is altered in patients with psoriasis. Using flow cytometry, we confirmed that the number of human M-MDSCs (CD11b+CD14+HLA-DR-) was remarkably increased in the peripheral blood of patients with psoriasis (Fig. 2A-B, p = 0.0065). Next, immunofluorescence staining of CD14+HLA-DR- M-MDSCs in the inflamed skin of patients with psoriasis revealed that the infiltration of M-MDSC cells in psoriatic skin tissue increased significantly compared to that in healthy controls (p < 0.01).