The neutralization of type IIFN biologic actions by anti-IFNAR-2 monoclonal antibodies is not entirely due to inhibition of Jak-Stat tyrosine phosphorylation

A panel of monoclonal antibodies (mAb) derived against human interferon-alp ha/beta receptor-2 (IFNAR-2) was evaluated for their ability to antagonize the biologic effects of type 1 interferons (IFN-alpha1, IFN-alpha 2a, and I FN-beta). Anti-IFNAR-2 mAb 117.7, 35.9, 53.2, and 51.44 neutralized type I IFN-mediated antiviral, antiproliferative, and major histocompatibility com plex (MHC) class I upregulation functions. However, only mAb 51.44 neutrali zed IFN-alpha 2a and IFN-beta -mediated natural killer (NK) cell cytotoxici ty. In BIAcore and cell binding studies, only mAb 51.44 and 234.28 inhibite d IFN-alpha 2a and IFN-beta binding to its receptor. The receptor blockade by mAb 51.44 and 234.28 resulted in the inhibition of IFN-alpha 2a and IFN- beta -induced tyrosine phosphorylation of Jak1, Tyk2, Stat1/2/3, and IFNAR- 1/2 and inhibition of IFN-stimulated gene factor 3 (ISGF3) formation. mAb 1 17.7, 35.9, and 53.2, although antagonists of IFN's biologic activities, di d not block the binding of IFN-alpha/beta to its receptor. The 117.7 mAb, r epresentative of this class of receptor nonblocking mAb, induced hyper-tyro sine phosphorylation of IFNAR-2 in the presence of IFN-alpha/beta but did n ot inhibit IFN-alpha/beta -induced Jak-Stat tyrosine phosphorylation and IS GF3 complex formation. These results show that the neutralization of type I IFN biologic actions by anti-IFNAR-2 mAb cannot be entirely explained by i nhibition of Jak-Stat tyrosine phosphorylation.