Quantitative aspects of T cell activation--peptide generation and editing by MHC class I molecules

The number of class I MHC/peptide complexes on the surface of antigen presenting cells crucially influences the activation of T cells. The formation of these complexes depends on selection processes at the level of peptide generation from proteins (predominantly in the cytosol), peptide transport into the ER and binding requirements of individual MHC class I molecules. These individual events have co-evolved to what is called 'antigen processing and presentation' and result in the representative presentation of peptides from every cellular protein by a species-specific combination of MHC class I molecules for recognition by MHC class I-restricted T cells.