Figure 2.

Schematic diagram of classes I and II MHC structures. The peptide-binding cleft is formed by the membrane-distal domains in both MHC molecules. In class I molecules, the membrane-distal domain is composed of the α1 and α2 regions whereas in the class II molecules, the membrane-distal domain is composed of the α1 and β1 regions. In class II molecules, the β2 region also plays a part in the variation of the peptide-binding cleft regions.