1. From the Clinical Gene Therapy Branch, National Center for Human Genome Research; the Leukocyte Cell Biology Section, National Institute of Arthritis and Musculoskeletal and Skin Disease, National Institutes of Health, Bethesda, MD; the Department of Pediatrics, University of Brescia, Brescia, Italy; and the Istituto di Tecnologie Biomediche Avanzate, CNR, Milan, Italy.