1. Laboratory of Tumor Immunology and Biology, National Cancer Institute, Bethesda, MD 20892.
2. Laboratory of Statistical and Mathematical Methodology, Division of Computer Research and Technology, National Institutes of Health, Bethesda, MD 20892.
3. Centre René Huguenin, 92211 St. Cloud, France.
4. Laboratory of Tumor Immunology and Biology, National Institutes of Health.