A Brief History of the International Histocompatibility Workshops
The field of human immunogenetics, a branch of genetics research focused on genes involved in the immune response, has been the subject of intense study for the last 35 years. This is especially true for that part of immunogenetics dealing with the major histocompatibility complex (MHC), a series of closely linked and highly polymorphic genes found in humans on chromosome number 6. The MHC genes and the cell surface protein molecules encoded by the MHC play a critical role in T cell recognition and function as antigens during transplantation.
Since the description of the first human leukocyte antigen group termed MAC in 1958, there has been rapid growth in the interest and knowledge about the genetic structure and biologic function of the MHC which in man is known as the Human Leukocyte Antigen (HLA) system. The dramatic advance in knowledge has been due largely to the early appreciation of the scope of work necessary to elucidate the HLA system requiring broad collaboration beyond what is possible within individual laboratories. This led to the organization of an international group of investigators willing to share reagents and unpublished data. The first HLA antigens were defined by individual groups using their own reagents, antisera and cell panels, identified locally. An exchange of reagents was necessary to compare antisera to standardize the definition of antigens and to establish a common nomenclature. The most pragmatic and effective way to promote this collaboration was through the organization of workshops designed to bring investigators together and to create the opportunity to exchange reagents for mutual study.
The first HLA workshop involved scientists from several countries and proved to be a seminal event, an impetus for more extensive collaborations in the following years. In addition to providing a mechanism for exchanging reagents, the International HLA Workshops have also been on the forefront of promoting new technology and disseminating both reagents and technical skills worldwide. This has been an invaluable resource for stimulating immunogenetics research and facilitating rapid translation of new technology and knowledge to patient care.
The International Histocompatibility Workshops: A Retrospective
First Histocompatibility Workshop: 1964
The First Histocompatibility Testing Workshop was organized by Dr. Bernard Amos and held in his laboratory at Duke University in Durham, North Carolina in June of 1964. Participants included 23 pioneering investigators actively engaged in the study of the recently discovered human “leukocyte antigens.” The workshop was convened for the purpose of comparing the different in vitro assay systems used at the time to define antigens which were described as Hu-1 (Dausset and Ivanyi), LA (Payne and Bodmer), and Four (van Rood). Among the assay methods studied in the “wet workshop” format at Duke were serology (including agglutination, cytotoxicity, leukocyte and platelet complement fixation, and mixed hemabsorption), the mixed lymphocyte culture reaction, the normal lymphocyte transfer test, and skin grafting. For the serology “component”, very few sera were available for testing, and participants in the wet workshop were only able to study six sera consisting of one ml each! It was at this workshop that Paul Terasaki introduced the microcytotoxicity test for serologic typing, and described the first positive leukocyte antibody crossmatch test associated with hyperacute renal graft rejection. The results of the first workshop were modest from the technical and reproducibility standpoints but the potential power of this collaborative work was very apparent and everyone agreed that an important step had been taken in establishing a spirit of international cooperation. Thus began the commitment to sharing reagents, standardizing methods and accepting a common nomenclature.Reference: Histocompatibility Testing: Report of a Conference and Workshop. Washington DC: National Academy of Sciences – National Research Council, 1965.
In addition, an informative and insightful first-hand account of the first workshop by its organizer and chief proponent can be found in: Amos DB. HLA – A Mouser’s Recollections. In: History of HLA: Ten Recollections. Terasaki PI (ed.), Los Angeles: UCLA Tissue Typing Laboratory, 1990: 61-97.
The Second Histocompatibility Workshop: 1965
The Second Histocompatibility Testing Workshop, organized by J.J. van Rood, was held in Leiden, Netherlands in August of 1965 and brought together 71 participants with an interest in further extending knowledge of human leukocyte antigen systems. This workshop set the format for future workshops: the study of a well-characterized cell panel (provided by van Rood) by different laboratories using their own sera and their own techniques. The 1965 workshop also saw the introduction of the computer to permit rapid analysis of the complex results obtained from many serologic reactions. By analyzing both family and population data, it was shown that most of the antigens recognized in the workshop belonged to a single genetic system, for which there was still no standardized nomenclature. The workshop included a study of skin grafting experiments, and it was demonstrated by this method that the antigens being studied behaved as transplantation antigens.Reference: Histocompatibility Testing 1965. Copenhagen: Munksgaard, 1965.
The Third Histocompatibility Workshop: 1967
The Third Histocompatibility Testing Workshop was organized by R. Ceppellini and was held in Torino, Italy in June of 1967 and included 110 participants. A workshop cell panel derived from eleven families and 21 unrelated donors was studied by 16 teams using 476 antisera. Thirteen different specificities were identified in independent fashion by the teams. The results of this combined effort, clearly and elegantly summarized by Ceppellini in a landmark chapter published in the Workshop Proceedings, demonstrated unequivocally that the antigens under study belonged to a single genetic system, with two subloci. Following the workshop (September, 1967), it was decided to name this system HL-A to designate it as the major system of leukocyte antigens in man.Reference: Curtoni ES, Mattiuz PL, Tosi RM, eds. Histocompatibility Testing 1967. Copenhagen: Munksgaard, 1967.
The Fourth Histocompatibility Workshop: 1970
The Fourth Histocompatibility Workshop, organized by Paul Terasaki, was held in Los Angeles in January of 1970 and brought together fifteen different laboratories testing 116 highly selected antisera. This was the first workshop in which antisera were exchanged by mail and in which each participating laboratory used a standard microlymphocytotoxicity assay. The results of the workshop established the existence of 11 official HL-A specificities (HL-A1, 2, 3, 5, 7, 8, 9, 10, 11, 12 and 13), and at least eight other specificities that were given given provisional designations (e.g., W27). Thorsby, Sandberg and Kissmeyer-Nielsen provided evidence of a third (HLA-C) locus, and Boyum’s method using ficoll hypaque for mononuclear cell separation was first used in a workshop format.Reference: Terasaki PI, ed. Histocompatibility Testing 1970. Copenhagen: Munksgaard, 1970.
The Fifth Histocompatibility Workshop: 1972
The Fifth Histocompatibility Workshop, organized by Jean Dausset and held in Evian, France in May of 1972, had as its major objective a world-wide population study of the HLA system. Forty-nine ethnic and racial groups were studied by 75 different laboratories using 118 selected antisera. Results from this workshop provided an important cornerstone of HLA frequency data for many of the world’s populations; much of this data is still referenced today. Ten new HLA designations, each given provisional nomenclature, were defined in the workshop: W16, W21, W23, W24, W25, W26, W29, W30, W31 and W32.
Reference: Dausset J, Colombani J, eds. Histocompatibility Testing 1972. Copenhagen: Munksgaard, 1973.
The Sixth Histocompatibility Workshop: 1975
The Sixth Histocompatibility Workshop, organized by F. Kissmeyer-Nielsen and held in Arhus, Denmark in June-July of 1975, had as its main objectives an investigation of the determinants and genetics of the MLR (subsequently termed the HLA-D locus) and the better identification and characterization of specificities belonging to the three previously-defined HL-A loci (subsequently termed HLA-A, B and C). This workshop was the first to include the use of D region homozygous typing cells (HTC) to study determinants of the HLA-D locus. A total of 62 HTC and 178 selected antisera were exchanged between participating laboratories. On the basis of workshop results, the WHO nomenclature committee named the first six HLA-D determinants. The first five HLA-C antigens were also named. At the Workshop Conference, numerous reports were made of HLA antigens that were expressed on B cells but not on T cells. These antigens were termed “Ia-like” or “D region associated B cell antigens”, and their description paved the way for the future description and characterization of the HLA-DR locus and the DR series of leukocyte antigens. A total of 15 new HLA specificities were given WHO designations following the workshop, including the first antigens defined at the HLA-C locus (Cw1-Cw5).
Reference: Histocompatibility Testing 1975. Kissmeyer-Nielsen F, ed. Copenhagen: Munksgaard, 1975.
The Seventh Histocompatibility Workshop:1977
The Seventh Histocompatibility Workshop, organized by Walter Bodmer and held at Oxford in September of 1977, carried forward a number of investigations: the serological study of the newly-described Ia (Immune-associated) determinants that were present on B cells but not on T cells, the relationship between the Ia specificities and Dw determinants defined by MLR and Dw homozygous typing cell (HTC) testing, the continued study of specificities belonging to the previously-defined HLA-A, B and C loci, and a study of a limited number of diseases to define their relationship with HLA-A, B, Dw and/or Ia specificities. For this workshop, the world was divided into 20 regions, each with its own regional officer, since there were too many participating laboratories to permit a central organization or data analysis. A total of 150 laboratories participated, studying 360 antisera, a panel of 13,000 lymphocytes covering all of the world’s major racial groups, and 54 homozygous typing cells. Based on workshop results, the HLA-DR locus, later shown to be part of the loosely-defined “Ia” antigen system, was officially defined, and a total of 26 new specificities were assigned WHO designations. In addition, evidence of a second Ia locus, termed MT by some laboratories and MB by others, began to emerge from this workshop. A total of 19 new HLA specificities were given WHO designations following the workshop, including the first seven antigens of the HLA-DR locus (DR1-DR7).Reference: Bodmer WF, Batchelor JR, Bodmer JG, Festenstein H, Morris PJ, eds. Histocompatibility Testing 1977. Copenhagen: Munksgaard, 1978.
The Eighth Histocompatibility Workshop: 1980
The Eighth Histocompatibility workshop, organized by Paul Terasaki and held in Los Angeles in February of 1980, was comprised of 130 participating laboratories testing 720 sera against 37,763 different cells. These studies allowed the HLA-DR locus to be more clearly defined and provided additional clarification of the newly-defined “MB” and “MT” specificities, which in subsequent workshops were shown to be encoded by genes of the HLA-DQ locus. There was also a cellular component, in which 31 laboratories used 115 selected homozygous typing cells to test cells from 2,565 individuals and 411 families. Because a large number of families were studied throughout the workshop, the data reference tables prepared from the results, giving gene, antigen and haplotype frequencies in 34 different ethnic groups, remained the standard benchmark throughout the next decade. Components of the workshop also dealt with the relationship between histocompatibility testing and transplantation outcome and studied the relationship between HLA and susceptibility to diseases such as diabetes, rheumatoid arthritis and multiple sclerosis. A total of 14 new specificities were given WHO designations following the eighth workshop.
Reference: Terasaki PI, ed. Histocompatibility Testing 1980. Los Angeles: UCLA Tissue Typing Laboratory, 1980.
The Ninth Histocompatibility Workshop: 1984
The Ninth Histocompatibility Workshop, organized by Ekkehard Albert and Wolfgang Mayr and held in Munich and Vienna in May of 1984, was comprised of 220 participating laboratories, organized into 21 regions throughout the world, testing 766 sera against cells derived from 2,300 families. Investigations into the association between HLA and susceptibility to 14 different diseases were continued. Based on data from the workshop, 14 HLA-A and B locus specificities were upgraded to full HLA status and 19 HLA-A, B, DR and DQ specificities were given provisional WHO designations (e.g., HLA-Aw66, Bw73, DRw13 and DQw3). The HLA-DQ locus was formally defined, replacing several local designations (DC, MB, MT) that had been used to describe alleles encoded by genes of this locus. At the workshop conference in Vienna, several papers describing the use of restriction fragment length polymorphism (RFLP) method to study HLA at the DNA level were presented, demonstrating the power and utility of DNA technology in HLA typing and paving the way for its use in subsequent workshops. In this workshop, the HLA-DP locus, with six specificities, was formally described, based on cellular typing using T cell clones.
Reference: Albert ED, Baur MP, Mayr WR, eds. Histocompatibility Testing 1984. Heidelberg: Springer-Verlag, 1984.
The Tenth Histocompatibility Workshop: 1987
The Tenth Histocompatibility Workshop, organized by Bo Dupont and held in New York City in November of 1987, had a number of specific objectives, including the standardization of assays used to characterize HLA genes and their products at the molecular, genetic, biochemical and cellular level, and the development of a reference panel of B-lymphoblastoid cell lines for factors of the HLA system. The workshop was divided into eight components, including serology, biochemistry, cellular and DNA sections. The serology component was organized into 34 different Antigen Groups to study antigen clusters of similar specificity. A total of 362 laboratories participated in the workshop. 
A large number of new HLA specificities were defined in this workshop by a variety of techniques: 62 new specificities were defined by serology; 94 alleles were defined by biochemistry (one-dimensional iso-electric focusing); and seven T-cell defined HLA-Dw specificities were defined using T cell clones. This workshop was the first to implement DNA-based HLA typing with the RFLP Southern blot methodology using a standard panel of cDNA probes for HLA class I and class II, with separate analysis of DRA, DRB, DQA, DQB, DPA and DPB. A total of 80 laboratories used RFLP to analyze the core workshop cell line panel as well as local samples. RFLP patterns were defined which corresponded with the serologically defined HLA class II alleles. Thus, DNA typing was established as a method for typing of HLA. Some changes in HLA nomenclature were made to accommodate the designation of HLA alleles, based on amino acid sequences deduced from gene sequences. The reference panel of 107 B-lymphoblastoid cell lines remains a reference resource for well-characterized HLA material to this day.
Reference: Dupont B, ed. Immunobiology of HLA. Histocompatibility Testing 1987, Vol. I, and Immunogenetics and Histocompatibility, Vol II. Springer-Verlag, New York, 1988.
The Eleventh Histocompatibility Workshop: 1991
The Eleventh Histocompatibility Workshop, organized by Kimiyoshi Tsuji and held in Yokohama, Japan in November of 1991, included 524 laboratories (of whom 244 submitted data for central analysis) from 53 different countries. The workshop was organized into six general components: serology, DNA typing, complement studies, anthropology, disease association, and transplantation. This workshop saw the widespread introduction of polymerase chain reaction (PCR) technology with sequence specific oligonucleotide probe (SSOP) hybridization as an HLA-DNA typing method. A total of 195 laboratories worldwide used the standard workshop panel of HLA class II primers and probes in transplantation, disease association and anthropological studies. Eighty-five of the B-lymphoblastoid cell lines from the 10th IHIWS reference panel were typed to the allele level for class II loci with the workshop PCR/SSOP reagents. In addition, a number of other HLA-DNA typing or matching techniques using PCR-amplified DNA were described, including the reverse dot blot, PCR-RFLP, hybridization protection, PCR heteroduplex formation, single-strand conformational polymorphism (SSCP) and direct sequencing assays. At the conclusion of the Workshop, it was decided that, in the future, all serological specificities would be named on the basis of correlation with an identified sequence, eliminating the need for a provisional “w” in the specificity designation. The report on Nomenclature for Factors of the HLA System, 1991, published in the workshop proceedings, listed 41 A-locus, 61 B-locus, 18 C-locus, 61 DRB1-locus, 14 DQA1-locus, 19 DQB1-locus, 8 DPA1-locus and 38 DPB1-locus alleles. The 87 new HLA allele sequences identified in the 11th Workshop provided further documentation of the extraordinary diversity of the HLA complex that can be detected by the multiplicity of DNA typing methods now available.
Reference: Tsuji K, Aizawa M, Sasazuki T, eds. HLA 1991. New York: Oxford University Press, 1992.
The Twelfth Histocompatibility Workshop: 1996
The Twelfth Histocompatibility Workshop, organized by Dominique Charron and held in St. Malo and Paris in June of 1996, consisted of seven major components: anthropology; HLA and cancer; transplantation; HLA and disease; new HLA genes; allele and haplotype societies; and DNA sequencing. Although serologic, biochemical and cellular methods were also studied, the focus of the workshop was the continued development and implementation of DNA-based typing methods for the analysis of HLA specificities at the allele level. PCR/SSOP typing, developed during the 11th Workshop, was used in the allele and haplotype society format to identify and characterize several new class II alleles. DNA sequencing-based typing for class I and class II genes was also investigated in several laboratories. A modification of the sequence specific priming (SSP) typing method, termed Amplification Refractory Mutation System (ARMS) typing, was used in the anthropology component to achieve low to medium resolution typing of HLA-A, B and C genes and high resolution typing of HLA-A*02 alleles. Important data on the distribution of A*02 alleles in various human populations was derived from these studies. Use of the ARMS method was also instrumental in a more comprehensive study of HLA-C alleles than had been possible by serologic methods, providing data on HLA-B/C linkage associations and clarifying a large number of Cw “blank” antigen assignments. Although final analysis of 12th Workshop data has yet to be completed, typing results for more than 26,000 individuals had been submitted by the end of May, 1996. Of this total, the anthropology component reported data on 11,650 individuals derived from 111 different populations.
Reference: Charron, D, ed. Genetic Diversity of HLA. Functional and Medical Implications. France: EDK, 1996
Author: Eric Mickelson. Special thanks to Paul Terasaki.