Neutralizing antibodies against IL-1α/β or KGF, GMCSF, and IL-6 abolished the mitogenic effect of F_PPARβ/δ. (A–C) Immunoblot analysis of epidermis from indicated OTCs treated with 400 ng/ml IL-1α/β (A), KGF, GMCSF, and IL-6 (B) neutralizing antibodies (each at 400 ng/ml) or 400 ng/ml preimmune IgG (C). Antibodies were added to OTC medium at each change of medium. Cell proliferation was measured using cyclin D1 and PCNA. Values below each band represent the mean fold differences in expression level with respect to K_CTRL from K_CTRL/F_CTRL OTC, which was assigned the value of 1. β-Tubulin served as a loading control. Representative immunoblots of epidermis from two indicated OTCs are shown.