Generation of tumor specific T lymphocytes by cross-priming with human dendritic cells ingesting apoptotic tumor cells

It has been suggested that dendritic cells (DCs) are capable of ingesting a poptotic tumor cells (ATCs) and presenting tumor-associated antigens to imm une cells. We evaluated the potential of human DCs, which have ingested ATC s, to serve as a source of antigenic epitopes for presentation to T cells s pecific for PCI-13, a squamous cell carcinoma of the head and neck cell lin e. Immature DCs (DCimm) generated in the presence of interleukin 4 and gran ulocyte machrophage colony-stimulating factor from peripheral blood monocyt es of HLA-A2(+) healthy donors were incubated in the presence of ATCs. Upta ke of ATCs by DCs was monitored by flow cytometry and confocal microscopy a fter 2-18 h of coincubation. When DCs were matured (DCmat) in the presence of proinflammatory cytokines, their capacity to uptake ATCs was reduced, Re sponses of PCI-13-specific CD8(+) T cells to unmodified PCI-13 cells and to DCimm or DCmat +/- ATCs or +/- tumor lysates were tested in gamma-IFN enzy melinked immunospot and cytotoxicity assays. Unmodified tumor cells were fo und to be the best stimulators of antitumor activity of the established T-c ell line, and ATCs alone were minimally stimulatory. However, DCs that inge sted ATCs were able to present tumor antigens to CTLs, and DCimm and DCmat were almost equally stimulatory. When DCs plus various tumor-derived prepar ations were used as antigen-presenting cells with autologous HLA-A2(+) T ce lls obtained from normal donors, DCs that had ingested ATCs were more effec tive in generating CD8(+) CTLs than tumor cells alone or DCs pulsed,vith tu mor lysates. The results indicate that human DCs fed with ATCs and then mat ured effectively generated T cell-mediated antitumor responses in vitro.