Despite limited clinical efficacy in large trials, dendritic cells (DC)-based immunization has yielded impressive responses in some patients. Key questions remain to be solved in order to optimize this therapeutic vaccine. Among them, the nature of the DC used and its state of maturation are pivotal. Besides myeloid DCs which are the cells essentially used in clinical trials, a new type of DC has been described resulting from the differentiation of monocytes in the presence of type I IFNs. In the present study, we analyzed the features of clinical grade type I IFN DC generated in the presence of either IL-3 (IL-3- DCs) or GM-CSF (GM-CSF-DCs) and compared their capacity to respond to poly I:C, a double-stranded RNA analog that mimics viral infection. The two DC types disclosed a similar immunophenotype characterized by high levels of costimulatory molecules, CCR7, HLA-class-I and class-II molecules. After poly I:C maturation, both DC types displayed a marked upregulation of CD80, CD83 and CD86. In addition, poly I:C stimulated them to secrete IFN-α IL-12 p70, IL-12 p40 and IL-6. Both DC types elicited potent allogeneic reactions. Priming of autologous T cells by IL-3-DCs or GM-CSF-DCs pulsed with an HLA-A2 restricted melan-A derived peptide, lead to expansion of melan-A specific CTL secreting high levels of IFN-γ and displaying a phenotype of memory cells. We conclude that mature clinical grade IL-3-DCs and GM-CSF-DCs share similar phenotype and functional properties including the capacity to prime Ag-specific CTL.

Author notes

Corresponding author