Tolerogenic IL-2 Containing Nanoparticles Induce CD4 and CD8 Regulatory T Cells and TGF-β Producing Regulatory NK Cells That Provide Essential Support for the Tregs Which Suppress Immune-mediated Disorders

Abstract Text: We have previously reported that a brief course of tolerogenic nanoparticles (NPs) decorated with anti-CD2 and containing IL-2 and TGF-β induced CD4 and CD8 iTregs and NK cells which had long-lasting protective effects from lupus-like disease in mice via a TGF-β-dependent mechanism. Using human peripheral blood mononuclear cells (PBMCs) to induce fatal graft-versus-host disease (GVHD) in NSG mice, we document here that TGF-β-producing NK cells induced by the tolerogenic NPs are essential for the development and maintenance of the Tregs and that the tolerogenic effects of IL-2 delivered by the NPs to the Tregs are TGF-β-dependent. Blockade of TGF-β signaling converted the tolerogenic response into an immunogenic response that markedly decreased the mice survival. Remarkably, the depletion of NK cells from the PBMCs had identical deleterious effects. In vitro stimulation of PBMC with either anti-CD2 or anti-CD3 antibody-decorated NPs induced most NK cells to express intracellular TGF-β. Importantly, the safety of the NPs was improved by eliminating the encapsulation of TGF-β since the NPs could locally stimulate target cells to produce the TGF-β for Treg induction. These results indicate for the first time, to the best of our knowledge, that NK cells can be induced to become essential tolerogenic cells and that the TGF-β produced by these cells associates with the long-lasting duration of the Treg therapeutic effects. This suggests that therapeutic agents which can concomitantly induce tolerogenic adaptive and innate responses have an increased ability to prevent and treat chronic immune-mediated inflammatory disease.