1. G. Ronzoni Institute for Chemical and Biochemical Research, 20133 Milan, Italy, Department of Anatomy, University of Bari, 70212 Bari, Italy, and Sigma-Tau Research Department, 0040 Pomezia, Rome, Italy, and Unit of General Pathology and Immunology, Department of Biomedical Sciences and Biotechnology, School of Medicine, University of Brescia, 25123 Brescia, Italy