The PathHunter Sargramostim Bioassay is an application of the DiscoverX Dimerization Assay platform, which can be used to detect ligand-induced functional dimerization of two subunits of a receptor-dimer pair. This assay detects GM-CSF-induced heterodimerization of the CSF2RA and CSF2RB receptors. The cells have been stably engineered to co-express CSF2RB fused to PK, and CSF2RA fused to EA. Binding of GM-CSF to the cytokine-specific CSF2RA receptor leads to heterodimerization with CSF2RB, leading to activation of intracellular signaling pathways. Receptor dimerization forces the two enzyme fragments to complement, resulting in the formation of a functional b-gal enzyme. The enzyme hydrolyzes a substrate to generate a chemiluminescent signal. Sargramostim binds to CSF2RA, stimulating receptor heterodimerization with the CSF2RB receptor, leading to an increase in 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.