The protein encoded by IL23R forms the receptor for the cytokine interleukin (IL)-23 that is part of a signaling pathway involving the gene product of another leprosy-associated locus, TNFSF15. Together with the IL-12 β1 subunit (encoded by IL12RB1), IL23R is a part of the IL-12, IL-23, and IFN-γ cascades, which have been suggested to play essential roles in immunity to mycobacteria [21]. This evidence concerns the gene IL23R and leprosy.