Fig. 1: IL-38 levels are reduced in skin and serum of psoriatic patients and upregulated by secukinumab treatment.

a IHC for IL-38, IL-36Ra, and IL-36γ (all stained in red-brown) was performed on paraffin-embedded sections of biopsies obtained from psoriatic skin (n = 8) including not lesional (NLS) (i), proximal-to-lesion (Pre-LS) (ii), lesional zones of evolving plaques, before (LS T0) (iii) and after 8 weeks (LS T8) (iv) of secukinumab treatment. Sections were counterstained with Mayer’s H&E. One out of eight representative stainings of psoriatic skin biopsies are shown. Bars, 100 μm. Graphs show the mean of four-stage score values for IL-38, IL-36Ra, and IL-36γ ± SD epidermal expression per three different fields of all six sections. *p ≤ 0.05, as assessed by Mann–Whitney U test. b mRNA expression of IL-38, IL-36Ra, and IL-36γ were analyzed by RT-PCR on healthy, NLS, LS T0, and LS T8 biopsies (n = 10) and normalized to HPRT-1 levels. c Cytokine levels were analyzed by ELISA in serum obtained by venous blood of healthy (n = 25) and psoriatic individuals (n = 25) before (Pso T0) and after (Pso T8) secukinumab treatment. b, c The results are shown as individual values and mean. *p ≤ 0.05; p** ≤ 0.01, as assessed by Mann–Whitney U test. d Correlation between the ratio of IL-36γ and IL-38 serum levels and PASI (psoriasis area and severity index) at baseline. e, f Correlations between the ratio of IL-38 or IL-36Ra between T8 and T0 and Δ PASI (Δ PASI, calculated as percentage of PASI reduction) score in psoriatic individuals after secukinumab treatment. Spearman’s test was used for correlation analysis. r indicates the strength of the linear relationship, n indicates the number of values in each plot, and p value shows the probability that the slope of the true relationship is zero. p ≤ 0.05 was considered significant