A Tertiary Twist to the Transglutaminase Tale
Figure 1
HLA-DQ2 and HLA-DQ8 Are Expressed on So-Called Antigen-Presenting Cells
The function of antigen-presenting cells (APCs) is to bind peptides derived from pathogens and “present” these to the T cells of the immune system. T cells detect such HLA–peptide complexes through their T cell receptors. In celiac disease, T cells respond to gluten peptides bound to HLA-DQ2 or HLA-DQ8. Gluten-derived peptides (red diamond) bind only with low affinity to HLA-DQ2 and HLA-DQ8, but TG2 can modify such peptides, which turns them into high-affinity binders. Consequently, the HLA–gluten peptide complexes are more stable, which facilitates and enhances T cell responses to such peptides.