1. Max-Planck-Institut für Zellbiologie, Rosenhof, Ladenburg, Germany.
2. Present address: Heinrich-Pette Institute for Experimental Virology and Immunology, Hamburg University, Hamburg, Germany.
3. Present address: Northern Community College, Science Division, Norfolk, Nebraska.
4. Present address: Department of Pathology, Conway Institute of Biomolecular and Biomedical Research, University College, Dublin, Ireland.
5. Present address: Institut für Immunologie, Medizinische Fakultät, Otto-von Guericke-Universität Magdeburg, Magdeburg, Germany.
6. Present address: Max-Planck-Institut für Medizinische Forschung, Heidelberg, Germany.
7. Present address: Institute for Cellular and Molecular Botany, Bonn University, Bonn, Germany.