Fig 2: The expression level of the IL-37 receptor IL-18Rα and binding partner IL-18BP in NC, OLK and OSCC tissues.(a) Immunohistochemical analysis of IL-18Rα and IL-18BP expression in NC, OLK and OSCC tissues. (b) Comparison of the staining score between these groups (*P < 0.05, **P < 0.01).

Fig 3: Relationship between IL-37 expression level and the degree of epithelial dysplasia in patients with OLK.(a) Immunohistochemical analysis of IL-37b expression in OLK lesions without epithelial dysplasia (top panels), with mild dysplasia (middle panels) and with moderate dysplasia (bottom panels). (b) Comparison of the staining score between these groups (***P < 0.001).

Fig 4: The expression of IL-37 in OSCC with or without metastasis ability.(a) Immunohistochemical analysis of IL-37b expression in OSCC patients with/without metastasis. (b) Comparison of the staining score between the two groups (*P = 0.004 < 0.01). (c) The expression of IL-37 mRNA in several cell lines detected by Q-PCR. (d) The expression of IL-37 protein (both pro-IL-37 and mat-IL-37) in several cell lines detected by Western blot.

Fig 5: IL‐37 inhibits the phosphorylation of IRAK4 and JNK downstream of SIGIRR and down‐regulates the expression of METTL14 by suppressing the activity of NF‐κB P65, thereby regulating the differentiation of CD4+ T cells. (A) The heatmap shows the differential expression of METTL3, METTL14, WTAP, FTO and ALKBH5 mRNA in RNA‐seq data of CD4+ T cells with and without IL‐37 (n = 3). (B) The mRNA expression levels of METTL3, METTL14, WTAP, FTO, and ALKBH5 in CD4+ T cells with and without IL‐37 were detected by RT‐qPCR (n = 3). (C) The protein expression levels of METTL3, METTL14, WTAP, FTO, and ALKBH5 in CD4+ T cells with and without IL‐37 were detected by WB. (D) The expression of METTL14 in CD4+ T cells after METTL14 overexpression virus infection was detected by RT‐qPCR (n = 3). (E) The m6A methylation abundance in CD4+ T cells after METTL14 overexpression virus infection was detected by dot blotting. (F) Flow cytometry shows that IL‐37 can counteract the differentiation shift of CD4+ T cell subsets Th1, Th2, Th17, and Treg caused by METTL14 overexpression (n = 3). (G) Flow cytometry was used to detect the interference effect of siRNA on SIGIRR expression in CD4+ T cells (left). The average fluorescence intensity of SIGIRR (right, n = 3). (H) The effect of IL‐37 on METTL14 expression in CD4+ T cells after SIGIRR knockdown was examined by Western blotting. (I) Flow cytometry was used to detect the inhibitory effect of P‐IRAK4 inhibitor on P‐IRAK4 expression in CD4+ T cells (left). The average fluorescence intensity of P‐IRAK4 (right, n = 3). (J) Western blot analysis of METTL14 expression in CD4+ T cells treated with IL‐37 after P‐IRAK4 inhibition. (K) Flow cytometry was used to detect the inhibitory effect of P‐JNK inhibitor on P‐JNK expression in CD4+ T cells (left). The average fluorescence intensity of P‐JNK (right, n = 3). (L) Western blot analysis of METTL14 expression in CD4+ T cells treated with IL‐37 after P‐JNK inhibition. (M) JASPAR online website was used to predict the potential binding Fragment of NF‐κB p65 and METTL14 gene promoter regions. (N) The potential binding Fragment of NF‐κB p65 and METTL14 gene promoter regions and their mutant sequences. (O) The fluorescence intensities of the wild‐type and mutant at Fragment 1, Fragment 2, and Fragment 3 after adding PBS and rhIL‐37 (n = 3). (p) Chromatin immunoprecipitation (ChIP) assay was performed to detect the binding of NF‐κB p65 to two fragments of the METTL14 gene. IgG was used as a negative control(n = 3). Error bars represent the mean ± SEM. n = 3 biologically independent experiments. * p < 0.05; ** p < 0.01; *** p < 0.001; **** p <0.0001; p values were calculated using Student's t test or One‐way ANOVA and Two‐way ANOVA.