The interleukin-23 receptor is a type I cytokine receptor. It is encoded in human by the IL23R gene.[5] In complex with the interleukin-12 receptor β1 subunit (IL-12Rβ1), it is activated by the cytokine interleukin 23 (IL-23).[6] The IL23R mRNA is 2.8 kilobases in length and includes 12 exons. The translated protein contains 629 amino acids; it is a type I penetrating protein and includes a signal peptide, an N-terminalfibronectin III-like domain and an intracellular part that contains three potential tyrosine phosphorylation domains.[6] There are 24 IL23R splice variants in mitogen-activated lymphocytes.[7]IL23R includes some single-nucleotide polymorphisms in the region encoding the domain that binds IL-23, which may lead to differences between people in Th17 activation.[8] There is also a variant of IL-23R that consists of just the extracellular part and is known as soluble IL-23R. This form can compete with the membrane-bound form to bind IL-23, modulating the Th17 immune response and regulation of inflammation and immune function.[9]