In a series of 131 monthly distributions of lymphocytes from 4 persons each, tissue typing done on a blind basis of 486 persons was examined for a 12-year period. The number of participating laboratories was initially 85 and 285 in 1987. 2. It was found that 21 HLA-A,B specificities could be identified by 95-100% of the laboratories. An additional 19 specificities were correctly identified by 80-94%. Less than 80% concordance was found for 27 specificities. 3. All of the 4 new specificities assigned by the WHO committee in 1987 were identified previously by the cell exchange. 4. We conclude that this ongoing program aids tissue typing laboratories throughout the world to standardize their typing reagents, to detect new specificities, to monitor progress in international dissemination of the key sera for antigen definition, and to evaluate the state of development of tissue typing to applications in kidney transplantation.
