Distinctive CD8 T cell activation by antigen-presenting plasmacytoid dendritic cells compared to conventional dendritic cells.

Plasmacytoid dendritic cells (pDCs) play a pivotal role in immune responses, particularly against viral infections. pDCs exhibit diverse functions, including interferon production, cytokine secretion, and antigen presentation. Here, we investigate the antigen cross-presentation capacity of pDCs and their role in CD8 T cell activation. Utilizing a culturing system with CD8 T cells and autologous pDCs derived from circulating CD34 hematopoietic stem and progenitor cells, we demonstrate that pDCs efficiently activate CD8 T cells via cross-presentation, promoting T cell expansion and cytotoxic activity. The antigen presentation capacity of pDCs is comparable to that of monocyte-derived dendritic cells (moDCs) and myeloid dendritic cells, which are known for their efficient antigen-presentation capacity. Transcriptomic analysis reveals genetic signatures in CD8 T cells activated by pDCs distinct from moDCs, suggesting different activation mechanisms. These findings underscore the importance of pDCs in antigen presentation and their contribution to CD8 T cell activation.