Abstract
Depending on how antigens are being decoded by dendritic cells (DCs), their acquisition will induce a homeostatic or immunogenic maturation program. This determines how antigens are being presented and whether DCs instruct T cells to induce tolerance or immunity. So far, the field lacks proper tools to distinguish the two maturation states. By using a lipid nanoparticle (LNP)-based approach and cellular indexing of transcriptomes and epitopes sequencing analysis, we designed a flow cytometry panel and transcriptional profiling tools to reliably annotate the two DC maturation states. The data corroborate that uptake of empty (or peptide-containing) LNPs induces homeostatic maturation in DCs, while uptake of Toll-like receptor ligand-adjuvanted (or mRNA-containing) LNPs induces immunogenic maturation, yielding distinct T cell outputs. This reveals that LNPs are not decoded as "dangerous" by DCs, and that the cargo is essential to provide adjuvant activity, which is highly relevant for the targeted design of LNP-based therapies.