Clusters of HLA class II beta restriction fragments describe allelic series

Eighty-eight HLA haplotypes have been investigated for the presence or absence of 52 restriction fragments generated by four restriction enzymes (EcoRI, EcoRV, HindIII, BamHI), and detected by a DQ beta cDNA probe. Correlation analysis showed several sets of positively associated fragments forming 11 clusters. They constitute three different allelic series. The first coincides with DR alleles, the second with DQ alleles, and within the third, one cluster coincides with DRw53 (MT). As shown by comparative hybridization, most fragments belonging to the DR- as well as the DQ-related series correspond to DQ beta genes. In contrast, the MT-related series corresponds to DR beta genes. The evolutionary significance of these restriction fragment clusters is discussed.