In a novel form of IFN-gamma receptor 1 deficiency, cell surface receptors fail to bind IFN-gamma (Jouanguy et al. 2000).The IFN-R1 and IFN-R2 chains are preassociated prior to ligand binding. In the absence of ligand the intracellular domains of the receptor chains are close to one another, preventing signal transduction as the intracellular components necessary for signaling are prevented from entering the receptor complex by the close proximity of the intracellular domains of these chains. Upon binding of the ligand IFN-gamma, the intracellular domains of the receptor chains move apart, opening the area for multiple molecules required for signal transduction to enter the receptor complex (Krause et al. 2002).