| Synthetic Long Peptide technology |
| 1. | The long peptide is taken up by the dendritic cell |
| 2. | The long peptide enters the proteosome, where it is degraded into small pieces, containing epitopes recognized by T cells. The epitopes are a mix of T helper (Th) epitopes and cytotoxic T cell (CTL) epitopes. The Th epitopes (red) enter the MHC Class II presentation pathway (3a). At the same time, the CTL epitopes (yellow) enter the MHC class I presentation pathway (3b). |
MHC class II presentation |
| 3a. | Th epitopes are transported to small compartments, containing MHC class II molecules, called endosomes. |
| 4a. | In the endosome the Th epitope binds to the MHC class II molecule. |
| 5a. | The MHC-epitope complex is expressed on the cell surface. The epitope presented by the MHC class II is recognized by the T cell receptor (pink) of a CD4 Th cell. |
| 6a. | The CD4 Th cell receptor binds to the MHC-epitope complex followed by binding of CD40 ligand (green) expressed on the Th cell to CD40 (blue) expressed by the DC. These interactions result in activation of the Dendritic Cell. |
| 7a. | The activated Dendritic Cell (DC) is thus licensed by the CD4 T cell to provide the appropriate signals to the CD8 CTL for full CD8 cytotoxic T cell activation. Furthermore, it signals to the CD8 CTL by release of soluble products to further stimulate CD8 T cell activation and expansion. |
MHC class I presentation |
| 3b. | The CTL epitopes enter the ER. |
| 4b. | In the ER, the CTL epitopes bind to newly formed MHC class I. |
| 5b. | The MHC-epitope complex is transported from the ER to the cell surface. |
| 6b. | The MHC-peptide complex is displayed on the cell surface. |
| 7b. | The MHC-peptide complex is recognized by the T cell receptor (green) on a CD8 cytotoxic T cell. At the same time, co-stimulatory molecules expressed on the DC (purple) interact with receptors for such co-stimulatory molecule (red). |
Outside the cell |
| 8. | These three signals (T cell receptor binding to MHC-epitope complex, co-stimulation and T helper signals) ensure optimal activation of the CD8 T cell. This activation leads to expansion of the CTL. |
| 9. | Active CD8 T cells will move to tumor cells that express the same epitopes. |
| 10. | The active CD8 T cells kill the tumor cells.
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