Differential Effects of Distinct Type I Interferons and IFN Inducers on Fc Receptor landscape and myeloid cell function

Antiviral monoclonal antibodies (mAbs) rely on Fc-mediated effector functions, which depend on interactions with Fc receptors (FcRs) expressed on immune cells such as monocytes and dendritic cells (DCs). While combinations of antiviral mAbs with type I interferons (IFN-I) or IFN inducers are being explored to enhance therapeutic efficacy, the impact of these immunomodulators on FcR expression remains poorly understood. In this study, we investigated the effects of IFN-2, IFN-{beta}, and the IFN-inducer TAK-981 (a SUMOylation inhibitor) on FcR modulation and functional activation in human monocyte subsets and monocyte-derived DCs (moDCs). Using flow cytometry and imaging techniques, we mapped the expression of activating Fc{gamma}Rs (CD64, CD32A, CD16A) and neonatal FcR (FcRn) under steady-state and stimulated conditions. We found that IFN-I selectively downregulates CD16A expression in classical monocytes while preserving other FcRs, whereas TAK-981 reduces FcRn expression in classical monocytes without affecting CD16A. Additionally, IFN-{beta} and TAK-981 but not IFN-2, selectively enhanced Fc{gamma}RI expression in moDC. IFN-{beta} also induced a stronger maturation and functional activation program in monocytes and moDCs compared with IFN-2, whereas TAK-981 largely reproduced the IFN-{beta}-driven phenotype and secretory profile. Furthermore, we demonstrated that IFN-I signaling alters the spatial distribution of FcRs, with IFN-{beta} and TAK-981 promoting distinct redistribution patterns of Fc{gamma}Rs in monocytes and moDCs. These findings reveal a novel layer of FcR regulation, highlighting that IFN-I and IFN inducers differentially modulate FcR expression, localization, and functional activation in a cell-type- and stimulus-specific manner. Overall, this work provides a framework for understanding how IFN-I-based immunotherapies may influence Fc-mediated immune functions while preserving FcRn-dependent antibody persistence.