1. Public Health Research Institute, New York, New York, 100161;
2. Colorado State University, Fort Collins, Colorado 805232;
3. National Institute of Public Health, N-0403 Oslo,3 and
4. Institute of Immunology, The National Hospital, N-0027 Oslo,4 Norway; and
5. Columbia University College of Physicians and Surgeons, New York, New York, 100325