CXCL1 and autoimmune disease: However, to investigate whether IL-17 receptor overexpression in co-cultured fibroblasts ensues in the activation of the receptor, a heteromeric structure made of at least one subunit IL-17RA that partners IL-17RC in IL-17A-mediated responses in autoimmune disorders (26), we investigated mRNA levels of several IL-17A target genes in the co-cultured fibroblasts, namely, CXCL1, CCL2, and CCL3, that were found increased by 29-fold, 11.9-fold, and 773.3-fold, respectively (p < 0.05) (Figures 2A–C).