The other side of the coin to increasing T cell responses for cancer therapy is reducing T cell responses in autoimmunity, and the mechanisms leading to such reduction may be highly relevant to immunosuppression in cancer. Xu et al. show that i.v. treatment of NOD/HLA-A02:01 mice with polystyrene bead nanoparticles coupled to epitope peptides relevant to human diabetes prevented onset of diabetic symptoms and extended survival. Xu et al. link marginal zone macrophage phagocytosis, CCL2 production, and recruitment of Treg cells and CD8+CD103+ dendritic cells to the mechanism of action.
AIMS/HYPOTHESIS: Induction of antigen-specific immunological tolerance may provide an attractive immunotherapy in the NOD mouse model but the conditions that lead to the successful translation to human type 1 diabetes are limited. In this study, we covalently linked 500 nm carboxylated polystyrene beads (PSB) with a mixture of immunodominant HLA-A*02:01-restricted epitopes (peptides-PSB) that may have high clinical relevance in humans as they promote immune tolerance; we then investigated the effect of the nanoparticle-peptide complexes on T cell tolerance. METHODS: PSB-coupled mixtures of HLA-A*02:01-restricted epitopes were administered to HHD II mice via intravenous injection. The effects on delaying the course of the disease were verified in NOD.beta2m null HHD mice. The diabetogenic HLA-A*02:01-restricted cytotoxic lymphocyte (CTL) responses to treatment with peptides-PSB were validated in individuals with type 1 diabetes. RESULTS: We showed that peptides-PSB could induce antigen-specific tolerance in HHD II mice. The protective immunological mechanisms were mediated through the function of CD4+CD25+ regulatory T cells, suppressive T cell activation and T cell anergy. Furthermore, the peptides-PSB induced an activation and accumulation of regulatory T cells and CD11c+ dendritic cells through a rapid production of CD169+ macrophage-derived C-C motif chemokine 22 (CCL22). Peptides-PSB also prevented diabetes in 'humanised' NOD.beta2m null HHD mice and suppressed pathogenic CTL responses in people with type 1 diabetes. CONCLUSIONS/INTERPRETATION: Our findings demonstrate for the first time the potential for using multipeptide-PSB complexes to induce T cell tolerance and halt the autoimmune process. These findings represent a promising platform for an antigen-specific tolerance strategy in type 1 diabetes and highlight a mechanism through which metallophilic macrophages mediate the early cell-cell interactions required for peptides-PSB-induced immune tolerance.