MHC class I and class II structures.

The basic structures of MHC class I and class II molecules are now well established. Over the past twelve months structural data on MHC class I molecules have provided details of the peptide binding groove for a number of alleles and have elaborated the mechanisms that allow binding of a range of peptides. Recent MHC class II structures have illustrated the mode of peptide binding both in mature complexes and in the MHC class II complex with a fragment of invariant chain (CLIP) during maturation.