IFN-gamma R beta chain is a 65 kD type I transmembrane protein, also known as accessory factor (AF-1) or IFN-gammaRII. IFN-gamma receptor is composed of an IFN-gamma R alpha chain (CDw119) and a beta chain. They are members of the class II cytokine receptor family. The alpha chain is required for ligand binding and ligand trafficking to the cells and also plays some role in signal transduction. The beta chain is critical for delivering IFN-gamma mediated pleiotropic signals. IFN-gamma R beta chain is broadly expressed on a variety of cells at low levels and upregulated on some activated B cells.