The UCLA International Cell Exchange has followed the progress in HLA typing since it began with 85 participating laboratories in 1974 and has expanded to 200 participants worldwide . The original goal of the Cell Exchange was to standardize the practice of HLA typing. This was an important undertaking because tissue typing for organ transplantation, disease studies, and population studies was dependent upon human typing sera obtained in very limited quantities, primarily from multiparous women. The accuracy of these reagents was dependent upon local methods of assessing the specificities of the anti-HLA antibodies and the volumes made it difficult to distribute sufficient quantities for use by everyone who performed HLA testing.

The Cell Exchange provided an alternative strategy, distributing the same cells to many laboratories for HLA typing. Each laboratory would report their results to UCLA and then receive a report of every other laboratory's results for comparison. This provided the laboratories a means for evaluating their typing results and for identifying the weaknesses in their panels of typing sera. As the complexity of the HLA system defined by antibody reagents grew, the Cell Exchange focused its efforts on providing challenging cell types - those that included "rare" HLA antigens or unusual combinations of antigens that might be difficult to discriminate.

A serum exchange was added in 1981, to check for anti-HLA antibody specificities. Accuracy of specificity and degree of sensitivity by various methods are assessed. Sera with complexes, interlocus antibodies, and reagent-quality antibodies are examined. This exchange helps labs detect problems in their serum screening panels and procedures.
In 1987, testing for Class II typing was initiated with the first shipment of 2 lymphoblastoid cell lines. In 1990, DNA-based typing results were first reported in correlation with the serologic results. Cells with rare alleles and unusual DR-DQ associations are studied. DRB1, DRB3, DRB4, DRB5, DQB1, DQA1, and DPB1 alleles are evaluated. These cell lines can be maintained in culture and used as reference lines.

In 1994, the Cell Exchange initiated offering the same cells for molecular typing as for serologic typing for Class I. The data from the parallel typings is instrumental in identifying serologic equivalents for Class I and Class II alleles that previously had little or no serologic information. This information is routinely added to the HLA Dictionary .
In 1997, DNA extracts from cells with unusual class I alleles were provided to participating laboratories. Many of these extracts were from the reference cells sequenced for rare alleles, thus giving laboratories the opportunity to type them, whereas they may not detect them in routine typing them in their local populations. Having these cells typed by numerous laboratories will help to achieve standardization in the typing of rare types.

In 2005, the International KIR Exchange was integrated within the framework of the International Cell Exchange, by offering reference DNA samples for KIR gene typing. The goals of this program are to standardize typing of KIR genes and alleles, and to identify new alleles.

In February 2007, a pilot study for MICA (class I chain-related molecule A) typing was initiated by sending samples to a select number of laboratories. This will provide an opportunity to compare typing results from different technologies. In the near future, this will expand to encompass MICA antibody identification. The goals are to standardize typing of MICA alleles and MICA antibody identification, as well as to identify new alleles.

In all the exchanges, the goals are to provide samples to validate methods and reagents, and to provide external quality control. By offering a forum for data exchange and discussion, the Cell Exchange has played a key role in international standardization. The UCLA International Cell Exchange has recorded the progress of HLA typing in a number of publications and presentations at national and international meetings.