from the Deutsche Forschungsgemeinschaft (DFG), by a BONFOR grant from the University of Bonn, and by Heisenberg Fellowship no. DFG NO454/3-I from the Deutsche Forschungsgemeinschaft (to NN). • 4-13 Reprints not available. Address correspondence to N Novak, Department of Dermatology, University of Bonn, Sigmund-Freud-Strasse 25,