1. Laboratory of Immunobiology, Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA.
2. Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
3. Immunobiology Section, Joslin Diabetes Center, Boston, MA 02215, USA.
4. Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK.