Phosphorylation of c-Src, which was shown to be activated by AhR ligands, was also increased by I3S and TCDD, and blocking of c-Src activity by 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo[3,4-d]pyrimidine (PP2) inhibited phosphorylation of both c-Src and STAT3, raising a possibility that stimulatory activities of I3S and << TCDD >> on Th17 differentiation could be exerted via increased phosphorylation of c-Src, which in turn stimulates [[ STAT3 ]] activation.