| Flap 1 |
Flap 2 |
| STEP 1 | Viral infection present; abonormal peptides |
| STEP 2 | --Class 1 MHC proteins incorporate abnormal peptides
|
| STEP 3 | Class 1 MHC proteins transported to cell membrane |
| STEP 4 | Abnormal peptides are displayed by class 1 MHC proteins on cell membrane |