Image from the RCSB PDB (www.rcsb.org) of PDB ID 3PGD (Gunther, S., Schlundt, A., Sticht, J., Roske, Y., Heinemann, U., Wiesmuller, K.H., Jung, G., Falk, K., Rotzschke, O., Freund, C.) (2010) Bidirectional binding of invariant chain peptides to an MHC class II molecule. Proc.Natl.Acad.Sci.USA 107: 22219-22224