1. Department of Laboratory Medicine,
2. Department of Pediatrics, and
3. Department of Surgery, University of California at San Francisco, San Francisco, CA;
4. Laboratory for Lymphocyte Differentiation, World Premier International Research Center, Immunology Frontier Research Center, Osaka University, Osaka, Japan; and
5. Laboratory for Lymphocyte Differentiation, Research Center for Allergy and Immunology, RIKEN, Yokohama, Kanagawa, Japan