Extended presentation of specific MHC‐peptide complexes by mature dendritic cells compared to other types of antigen‐presenting cells

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Abstract
Dendritic cells are known as the most potent antigen‐presenting cells for the induction of T cell‐mediated immune responses. To discriminate between the presentation of antigens and the co‐stimulatory aspects of this high immunostimulatory capacity, we used recombinant antibodies with T cell receptor‐like specificity to detect defined MHC‐peptide complexes on living cells. Mature human dendritic cells (mDC) were compared with immature DC (iDC), monocytes, CD4+ T lymphocytes, melanoma cells, T2 cells and B lymphoblastoid cells for their capacity to present MHC class I‐restricted tumor‐associated T cell epitopes and were found to display the specific peptides two to six times longer than other cells. The most short‐lived peptide had an average half‐life of 8.7 h on mDCvs. 3.5 h on B lymphoblastoid cells, while the most long‐lived peptide had a half‐life of 118.5 h vs. 20.7 h on these two cell types. The decay kinetics of specific MHC‐peptide complexes on iDC were among the fastest observed. The high potency of dendritic cells to induce specific T cell responses is thus based, in addition to the expression of co‐stimulatory molecules, on an extended antigenic memory, which increases the likelihood and the extent of contacts between dendritic cells and antigen‐specific T cells.