1. From the Department of Hematology, the Institute for Medical Informatics, Biometry and Epidemiology, and the Institute of Cell Biology, Medical Faculty, University of Essen; Gemeinschaftspraxis für Hämatologie und Onkologie Essen; Gemeinschaftspraxis für Hämatologie und Onkologie Velbert, Germany; and the Laboratory of Immunogenetics, Department of Genetics, Biology and Biochemistry, University of Torino, Italy.