HLA-A*1101/K b transgenic mice were produced at Pharmexa-Epimmune (San Diego, CA) and bred at the University of Chicago. These HLA-A*1101/K b transgenic mice express a chimeric gene consisting of the 1 and 2 domains of HLA-A*1101 and the 3 domain of H-2K b , and were created on a C57BL/6 background. For each test, we used 4-5 mice for each group. Each experiment was repeated 2 to 3 times. Experiments in Figure 7b were performed including a subgroup analyzed for immune response in parallel with a subgroup in the challenge shown. All studies were conducted with approval of the Institutional Animal Care and Use Committee at the University of Chicago.