1. Lymphocyte Biology Section, Division of Rheumatology, Immunology and Allergy, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, 1 and
2. Department of Pathology, University of Western Australia, Nedlands 6907, Western Australia, 2 and
3. Trescowithick Research Laboratories, Peter MacCallum Cancer Institute, Melborne 3000, Victoria, 3 Australia