Table 1.
Comparison of the major characteristics of the HLA class I and II APM pathway.
| Steps of APM | HLA class I APM | HLA class II APM |
|---|---|---|
| Antigen presentation | HLA-A, -B, -C | HLA-DR, -DQ, DP |
| Stabilization and loading | Tapasin | HLA-DM |
| Peptide generation | Proteasome subunits | Lysosomal enzymes |
| Transactivation | No | Yes, CIITA |
| Assembly and stabilization | β2-m | Invariant chain |
| Peptide loading compartment | ER | MCII |
| Presentation to | CD8+ T cells | CD4+ T cells |
| Regulation by cytokines | IFNγ | IFNγ |
| Expression by tumor cells | Loss Downregulation |
Loss Down- or upregulation de Novo expression |