(686b) Engineering Immune Tolerance through a Novel Strategy for Dendritic Cell Modulation

Dendritic cells (DCs) are key regulators of immune homeostasis and central targets for antigen-specific tolerance induction in autoimmune disorders and transplant medicine. Our work integrates two complementary immunoengineering strategies—Push/Pull Immunomodulation (PPI) and lymph node-targeted liposomal delivery—to induce tolerogenic DCs (tolDCs) and promote regulatory T cell (Treg) expansion. Previously, we identified three optimized PPI combinations (PPI-1, 7, and 9) capable of inducing tolDCs from murine bone marrow-derived DCs (BMDCs) through large-scale high-throughput screening of combinatorial immunosuppressant and TLR agonist libraries, leading to robust antigen-specific Treg induction.

To enhance translational relevance, we evaluated these formulations in human monocyte-derived DCs (moDCs) differentiated from peripheral blood mononuclear cells (PBMCs). Compared to 6 clinically relevant tolerogenic agents, PPI-treated moDCs exhibited superior expression of PD-L1 and BTLA, enhanced longevity (>10 days), and sustained tolerogenic phenotypes. PPI-9–treated moDCs specifically generated CD25^hi Tregs upon stimulation with antigenic peptide pools, but not with nonspecific CD3/CD28 stimulation, demonstrating antigen-specific immune modulation. Transcriptomic analysis further revealed distinct gene expression signatures in PPI-tolDCs, with upregulation of inhibitory cytokines and survival pathways compared to both natural and conventional induced tolDCs. We also developed liposomal PPI formulations for in vivo delivery.

Together, these findings support a modular strategy for tolDC immunomodulation and lay the groundwork for the development of tolerogenic therapies in translational clinical studies.