The PathHunter Tocilizumab Bioassay is an application of the DiscoverX Dimerization Assay platform. The assay is designed to detect the ligand-induced interaction of the interleukin-6 receptor (IL-6R) with the interleukin-6 signal transducer protein (IL-6ST). The cells have been engineered to co-express IL-6ST fused to PK, and IL-6R fused to EA. Binding of an agonist to the IL-6R causes multimerization of the IL-6R and IL-6ST receptors, resulting in activation of downstream signaling events. This brings the two b-gal fragments into close proximity, forcing complementation. Heterodimerization of the two receptor chains results in the formation of a functional b-gal enzyme that hydrolyzes the substrate to generate a chemiluminescent signal. Blocking IL-6 binding with an anti-ligand or anti-receptor antibody can prevent this interaction, resulting in a loss of signal.The bioassay kit contains all reagents needed for the assay, including pre-qualified cryopreserved cells, detection reagents, cell plating reagent, positive control agonist, and assay plates.