The Cell Exchange has helped laboratories to sharpen their skills and has monitored and published the development of tissue typing over the years. The goal of providing unusual types or combinations to participants was often accomplished by identifying cells that gave ambiguous or incomplete results. Many of these cells were provided to the Cell Exchange by the participating laboratories and often these challenging HLA types were found to include "variants," which represented new alleles that were not defined by serology.
The problem of how to ship viable lymphocytes to locations throughout the world was solved by Dr Min Sik Park in 1973 (Park MS and Terasaki PI, Transplantation (1974) 18, 520-524) and permitted the evolution of international testing. This simple method is still used today by organizations involved in proficiency testing as well as for routine exchanges of material among laboratories.
Over the years, the Cell Exchange has helped to identify numerous new or rare antigens. In the course of standardizing specificities to attain international agreement, the exchanges have identified duplicate names for the same specificity and the same name being used for different ones, for example, A26 versus A66 for the antigen encoded by A*6601, and A34 versus A66 for the one encoded by A*6602.
More than 30 cells typed in the Cell Exchange now serve as reference cells for Class I alleles, confirmed through subsequent study. Examples of variants which were extensively studied in previous cell exchanges and received formal designations by the WHO Nomenclature Committee are: A9.3 (A*2403), BN21 (B*4005), B5.35 (B*5102), 5Y/8w58/BSNA (B*7801, B*7802), numerous B15 variants (B*1508, B*1511, B*1512, B*1515), and DT (B*8101). The Cell Exchange data has provided vital correlation between alleles and serologic names in many cases, such as establishing B*1518 as B71 and Cw*1701 as a short Cw7. Among the numerous alleles detected in exchange cells were A*1104, A*6803, B*1304, and B*4012. Our Cell Exchange continues to study serological variants not yet recognized and bring them to the forefront for validation by sequence analysis.
By routinely contributing data to be used in the HLA Dictionary that offers allele-serologic equivalents, the Cell Exchange provides valuable information to be used in matching searches for unrelated donors in databases with mixtures of data attained using different techniques. This is important during the transition period as labs migrate to the exclusive use of molecular testing methods.
The International Cell Exchange has a long and consistent history of service to the histocompatibility community. The Cell Exchange has operated continuously for more than thirty years, sending cells and sera, accounting for more than 3000 reference samples. The close of 2006 will mark the completion of 322 cell exchanges, encompassing 1288 cells for Class I serology, 920 sera for anti-HLA antibody identification, 386 cells for Class II serology, 310 cells for Class II DNA typing, and 464 cells for Class I DNA typing. The exchange has also provided 376 DNA extracts for HLA Class I testing.
