1. Laboratory of Tumor Cell Biology, National Cancer Institute, Bethesda, Maryland 20205
2. Department of Cell Biology, Litton Bionetics, Inc., Kensington, Maryland
3. Laboratory of Human Carcinogenesis, National Cancer Institute, Bethesda, Maryland 20205
4. Department of Pathology, New York Veterans Administration Hospital, New York 10010
5. Department of Immunologie, H6pital Raymond Poincaré, 92380 Garches, France