FastDC derived from human monocytes within 48 h effectively prime tumor antigen-specific cytotoxic T cells.

Previously, we have shown that dendritic cells (DCs) with full T-cell stimulatory capacity can be derived from human monocytes after 48 h of in vitro culture (FastDC). Compared to a standard 7-day protocol, this new strategy not only reduces the time span and the amount of recombinant cytokines required, but may also resemble DC development in vivo more closely. Using a melanoma antigen model, we show here that FastDC prime CTL responses against tumor antigens as effectively as standard monocyte-derived DCs (moDCs). FastDC and moDCs derived from monocytes of HLA-A2(+) donors were loaded with the melanoma-associated, HLA-A(*)0201-restricted peptide Melan-A and cocultured with autologous CD3(+) T cells. After two weekly restimulations with freshly prepared, peptide-loaded FastDC or moDCs, binding of CD8(+) T cells to fluorescently labeled MHC-I/Melan-A-peptide complexes and intracellular cytokine staining revealed that the two DC preparations had an equal capacity to prime Melan-A-specific, IFN-gamma producing CD8(+) T cells. CTLs derived from cocultures with FastDC lysed Melan-A-loaded T2 cells even more effectively than CTLs primed by moDCs. Comparative analysis also revealed that FastDC possess an equal capacity to migrate in response to the chemokine receptor CCR-7 ligand 6Ckine. Importantly, DCs can be generated with higher yield and purity using the FastDC-protocol. The reliability and efficacy of this new strategy for DC development from monocytes may facilitate clinical investigation of DC-based tumor immunotherapy.