Cross-presentation of glycolipid from tumor cells loaded with α-galactosylceramide leads to potent and long-lived T cell–mediated immunity via dendritic cells

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Abstract
We report a mechanism to induce combined and long-lived CD4+ and CD8+ T cell immunity to several mouse tumors. Surprisingly, the initial source of antigen is a single low dose of tumor cells loaded with α-galactosylceramide (α-GalCer) glycolipid (tumor/Gal) but lacking co-stimulatory molecules. After tumor/Gal injection intravenously (i.v.), innate NKT and NK cells reject the tumor cells, some of which are taken up by dendritic cells (DCs). The DCs in turn cross-present glycolipid on CD1d molecules to NKT cells and undergo maturation. For B16 melanoma cells loaded with α-GalCer (B16/Gal), interferon γ–producing CD8+ T cells develop toward several melanoma peptides, again after a single low i.v. dose of B16/Gal. In all four poorly immunogenic tumors tested, a single dose of tumor/Gal i.v. allows mice to become resistant to tumors given subcutaneously. Resistance requires CD4+ and CD8+ cells, as well as DCs, and persists for 6–12 mo. Therefore, several immunogenic features of DCs are engaged by the CD1d-mediated cross-presentation of glycolipid-loaded tumor cells, leading to particularly strong and long-lived adaptive immunity.
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