Fig. 4

Recombinant IL-38 proteins do not globally affect IL-1α-induced IL-8 production in IL-36R HEK Blue and NHK cells. A. NHK and B. IL-36R HEK Blue cells were preincubated with recombinant human IL-38 variants (aa2-152 with C-terminal His tag; aa2-152; aa3-152; aa20-152 IL-38:Fc-KIH fusion protein) at indicated concentrations (10-3000 ng/ml, corresponding to 0.4–58.8 nM; see Table 1), before stimulation with IL-1α (1 ng/ml, corresponding to 0.06 nM) for 24 h. IL-8 production was assessed by ELISA in culture supernatants. Recombinant human sIL-1Ra (1-100 ng/ml, corresponding to 0.06–5.9 nM) and recombinant icIL-1Ra1 (1-100 ng/ml, corresponding to 0.06–5.6 nM) were used as positive controls to inhibit IL-1α. Recombinant human IL-36Ra (10-1000 ng/ml, corresponding to 0.6–58.8 nM) was used as a negative control. Results are expressed in % of the IL-8 production observed with IL-1α alone. Each dot represents the mean of 3 technical replicates in an independent experiment. Results are shown as individual values and mean ± SEM for 5 (A) or 3 (B) independent experiments. **p < 0.01, ***p < 0.001, ****p < 0.0001 vs. IL-1α alone, as assessed by ANOVA, followed by Dunnett’s multiple comparisons test