1. Experimental Immunology Branch, National Cancer Institute (NCI), National Institutes of Health (NIH), Bethesda, MD 20892
2. Max Planck Institut fur Biochemie, 82152 Martinsried, Germany
3. Adolf Butenandt Institut fur Physiologische Chemie, Physikalische Biochemie und Zellbiologie, Ludwig Maximilians Universitat, 80336 Munich, Germany