IL23R and rheumatoid arthritis: The function of the IL-23 receptor is modulated by natural genetic variation, for instance, at the single-nucleotide variant (SNV) rs11209026-G/A (R381Q) in the coding sequence of IL23R. The derived (and minor) A-allele has shown strong protective effects against immune-related diseases in European populations (e.g., CD, UC, ankylosing spondylitis, rheumatoid arthritis, psoriasis).4