1. Department of Biopathology, University of Palermo, 90134 Palermo, Italy
2. Laboratory of Immunology, National Institute for Infectious Diseases “L. Spallanzani,” 00149 Rome, Italy
3. Max-Delbruch Center for Molecular Medicine, 13122 Berlin-Busch, Germany
4. Institute of Biomedicine and Molecular Immunology, National Research Council, 90134 Palermo, Italy