DNA analysis of histocompatibility antigens: fragments from the recently identified DR loci

1. The DR locus of class II histocompatibility antigens (HLA-DR) is routinely typed by microlymphocytotoxicity tests. However, the preparation of good antisera is a complex process which relies heavily on a well-defined cell panel. 2. We have studied homozygous typing-cells representing the most common DR specificities in order to determine their typing pattern at the DNA level. 3. Restriction fragment length polymorphism obtained using six restriction enzymes permitted us to identify most of the DR specificities, including recently described splits of the DRw6. Specific fragments were tentatively allocated to the three DRw52 alleles. 4. The number of beta genes present on DRw52 and DRw53 antigen carrying cells is also discussed.