All experimental procedures involving animals were approved by the University of Melbourne's animal ethics committee under the AEC numbers 0707207 and 061061. HLA-A2k b transgenic mice (HHD mice) were obtained from the Queensland Institute for Medical Research and bred in the Animal House Facility of the Department of Microbiology and Immunology at The University of Melbourne under specific pathogen free conditions. These mice do not express H-2D b but instead express the chimeric monochain of the a1 & a2 domains of HLA-A2.1 and the a3 cytoplasmic and transmembrane domains of H-2D b linked at its N-terminus to the C terminus of human b2 microglobulin [28] .