Fig. 1: The antimicrobial peptide cathelicidin induces IL-17A production by CD4⁺ T cells.

Splenocytes isolated from C57BL/6 J mice were cultured in Th17-driving conditions for 48 h in the presence or absence of 2.5 μM murine cathelicidin. A, B Expression of cytokines was determined by intracellular flow cytometry. C Splenocytes were cultured with αCD3αCD28 stimulation alone with cathelicidin. D Production of IL-17A following increasing doses of cathelicidin (for 48 h) and E prodution over increasing days in culture was assessed. F Geometric mean of IL-17A expression was also assessed at 48 h. G After 72 h of culture supernatant was collected and IL-17A protein quanitified by ELISA. H Representative flow cytometry plots showing RORγt expression; I RORγt expression was quantified over time in culture. J At 48 h in culture all IL-17⁺ cells were RORγt⁺. K Sorted CD4⁺ T cells were cultured alone in Th17-driving confitions for 48 or 72 h. L–N Following 24 h culture of sorted CD4⁺ T cells STAT3 phosphorylation was assessed by flow cytometry. Data shown are individual mice used in separate experiments with line at median. Statistical signficance was determined using a one-way ANOVA with Sidak’s post-test (E, I), a two-tailed paired t-test with no corrections (B, G, F, G, K, M, N) or a one-way ANOVA with a Dunnett’s multiple comparison post-test (D). N values: B - 17, C - 6, D - 3, E - 6, F - 24, G - 7, I - 6, K - 4, M - 3, N - 3. Black symbols represent untreated samples and open symbols represent samples exposed to cathelicidin.