Cytokine receptor families that utilize Janus kinase (JAK) enzymes for signaling. Cytokines are small proteins secreted by cells that can produce a variety of responses such as growth, development, differentiation, and activation of immune cells as well as nonimmune cell types. Cytokines exert these biological effects by binding to receptors on the surface of cells. Several cytokine receptors rely on the association and activation of JAK enzymes on the cytoplasmic portion of the receptor in order to transmit signals to the nucleus and induce necessary changes within the cell. Cytokine receptors can be groups according to the types of JAKs that are recruited to the receptor complexes. Many cytokines involved in allergy, inflammation, and pruritus bind receptor complexes that utilize JAK1. For example, IL-2 and IL-4 will bind receptor complexes that recruit JAK1 and JAK3. IL-6 and IL-13 bind receptors that engage JAK1, JAK2, and TYK2, and IL-31 will engage receptors that activate JAK1 and JAK2. In contrast, several cytokines involved in hematopoiesis (GM-CSF, erythropoietin) or innate immune cell defenses (IL-12 and IL-23) activate receptors dependent on JAK2/JAK2 or JAK2/TYK2 pairings. Oclacitinib (APOQUEL(®)) is a novel Janus kinase inhibitor with activity against cytokines involved in allergy. Gonzales AJ, Bowman JW, Fici GJ, Zhang M, Mann DW, Mitton-Fry M - Journal of veterinary pharmacology and therapeutics (2014). Not Altered. CC.