[1] Univ Reading, Sch Anim & Microbial Sci, Reading RG6 6AJ, Berks, England
[2] Univ Sheffield, Dept Mol Biol & Biotechnol, Sheffield S10 2UH, S Yorkshire, England
[3] Henry M Jackson Fdn, Rockville, MD 20850 USA
[4] Inst Pasteur, IBL, CNRS UMR 319, F-59021 Lille, France
[5] Stanford Univ, Sch Med, Dept Med, Div Oncol, Stanford, CA 94305 USA