1. Department of Immunology, Stephan Angelov Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria.
2. Research Division of Immunology, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA.
3. Department of Medicine and Pathology, Winthrop P. Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.