Fig. 2 ∣. Approaches for the induction of antigen-specific immune tolerance.
Cell-based approaches include the ex vivo induction of tolerogenic dendritic cells (DCs), apoptotic cells or regulatory T cells engineered to express chimeric antigen receptors (CAR Treg cells), all of which can be designed to deliver antigen with or without an immunomodulatory signal. Viral particle approaches include the delivery of DNA-encoded or RNA-encoded antigen via adenoviruses, lentiviruses or plant viruses. Synthetic particles, including metallic, polymeric, lipid-based (including liposomes or lipid nanoparticles), peptide–polymer, dendrimer or polyelectrolyte particles, can be designed to co-deliver antigens, antibodies and immunomodulators, in various combinations. Alternatively, antigens can be delivered via toxin-bound MHC molecules to induce the death of antigen-specific cells, and albumin, antibodies or nanoemulsions can deliver antigens and immunomodulators to induce antigen-specific immune tolerance. FASL, FAS ligand; PEG, polyethylene glycol.