On the cover: Pocket 4 of HLA-DRB4*01:01 with anchor residue Glu (space-filling). DRB4 residues are in stick form with transparent surfaces colored according to atom charge. This pocket is quite restrictive (favoring Gln/Glu), but in one scenario accepts Trp, allowing presentation of a unique proinsulin epitope. James, E. A., L. Gillette, I. Durinovic-Bello, C. Speake, G. P. Bondinas, A. K. Moustakas, C. J. Greenbaum, G. K. Papadopoulos, and W. W. Kwok. 2018. DRB4*01:01 has a distinct motif and presents a proinsulin epitope that is recognized in subjects with type 1 diabetes. J. Immunol. 201: 3524–3533.