1. Repligen Corporation, Cambridge, MA 02139.
2. Department of Surgery, Duke University Medical School, Durham, NC 27710.
3. Office of Director, National Cancer Institute-Frederick Cancer Research Facility (NCI-FCRF), Frederick, MD 21701.
4. Laboratory of Tumor Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
5. Centocor, Malvein, PA 19355.
6. Central Research and Development Dcpartment, Experimental Station, E. I. du Pont de Nemours & Co., Inc., Wilmington, DE 19898.