From the Departments of Pathology (D.-F.D., M.V., K.G., G.M.M., L.A.L., P.S.R.), Physiology and Biophysics (L.F.S.), Genome Sciences (D.M.T., M.J.M.), Biostatistics (M.J.E.), and Comparative Medicine (W.C.L.), University of Washington, Seattle. (At 2009-06-02)