Translational Opportunity of Engineered IFNγ-eEVs Through Targeted Inhibition of JAK/STAT1 Signaling, Mimicking IVIg Therapy

Immunoglobulin (Ig) replacement therapies (IgRT) including intravenous (IVIg) and subcutaneous (SCIg), are pooled IgG preparations widely used to restore humoral immunity and to suppress pathological inflammation in autoimmune and inflammatory disorders. Despite broad clinical use, the mechanisms underlying their immunomodulatory effects remain incompletely defined. Here, we identify extracellular vesicle (EV)-associated cytokines as mediators of IVIg activity. Multiplex bead-based flow cytometry revealed that EVs isolated by size exclusion followed by ultracentrifugation from IVIg were CD63 positive but depleted of platelet-derived and HLA markers relative to EVs from unprocessed human plasma. Luminex profiling demonstrated substantial reduction of pro-inflammatory cytokines in IVIg EVs. Notably, although IVIg EVs contained abundant IFNγ, they failed to activate IFNGR/JAK/STAT1 signaling. Instead, prolonged exposure to IVIg EVs suppressed subsequent IFNγ-induced STAT1 activation. Engineered IFNγ-coated EVs (IFNγ-eEVs) recapitulated both activating and inhibitory effects indicating context-dependent signaling bias. Critically, cold ethanol precipitation, a key step in IVIg manufacturing, selectively abrogated the activating function of IFNγ-eEVs while preserving their inhibitory capacity. These findings define a previously unrecognized mechanism where IVIg processing generates EVs that bias IFNγ signaling toward suppression. EV-associated cytokines therefore represent a generalizable pathway through which IVIg exerts anti-inflammatory effects across immune-mediated diseases.