The high-affinity IFN-gamma receptor complex is made up of two type I membrane proteins, IFN-gammaR1 (IFN gamma R alpha ) and IFN-gammaR2 (IFN-gamma R beta ). IFN-gamma R1 is the ligand-binding subunit that is necessary and sufficient for IFN-gamma binding and receptor internalization. IFN-gammaR2 is required for IFN gamma signaling but does not bind IFN-gamma by itself. A genetic variation in IFNGR1 is associated with susceptibility to Helicobacter pylori infection. In addition, defects in IFNGR1 are a cause of mendelian susceptibility to mycobacterial disease, also known as familial disseminated atypical mycobacterial infection.