CCL26 mRNA expression in HaCaT cells was determined by RT-PCR when they were stimulated with IL-4, leflunomide, JAK inhibitor 1 and JAK3 inhibitor 1. Leflunomide and JAK inhibitor 1, but not JAK3 inhibitor 1, inhibited IL-4-enhanced CCL26 mRNA expression dose-dependently. When the reverse transcriptase enzyme was omitted, neither CCL26 mRNA nor G3PDH mRNA was detected.