Fig. 3. MHC structures and peptide presentation.

The HLA-DQ molecule is an αβ heterodimer of MHC class type II. The three-dimensional shape of the peptide-binding groove is formed by the combination of α and β chains, which are genetically encoded by the HLA-DQA1 and HLA-DQB1 alleles respectively⁸¹. The structure of the peptide-binding groove determines which peptides (foreign or self) are presented at the cell’s surface⁸¹, as is shown in the schematic. As an example, in coeliac disease, patients possess HLA alleles that encode for peptide binding grooves with structures suited to the presentation of gluten-derived peptides⁸².