1. Immunology Area, Pediatric Hospital Bambino Gesù, Viale San Paolo 15, 00146 Rome, Italy
2. Department of Experimental Medicine, Section of Histology, University of Genova, Via G.B. Marsano 10, 16132 Genova, Italy
3. Department of Medicine, University of Verona, Piazzale L.A. Scuro 10, 37134 Verona, Italy