Kupffer cells are key mediators of antigen-specific immune tolerance by peptide-coupled red blood cells.

Induction of antigen-specific immune tolerance is the most precise method for reverting an autoreactive immune response in diseases such as multiple sclerosis (MS). Coupling red blood cells (RBCs) with a cocktail of MS immunodominant peptides is a promising approach to induce antigen-specific immune tolerance in patients. Here, we show that RBCs coupled with disease-inducing antigen efficiently prevent the development of experimental autoimmune encephalomyelitis, when administered prophylactically, and ameliorate disease symptoms when given therapeutically. The tolerogenic activity of peptide-coupled RBCs (pcRBC) was antigen specific and dependent on both cell and peptide dose. Kupffer cells (KC) were the primary phagocytes of pcRBC, and their uptake of pcRBC did not require complement component 3, SIRPα, and Stabilin 1 and 2. KC were indispensable for the induction of tolerance, which was accompanied by programmed death-ligand 1 up-regulation and a tolerogenic transcriptional shift. Our findings establish KC as central mediators of pcRBC-induced immune tolerance and provide mechanistic insight for the use of this therapeutic strategy in autoimmune disease.