Allogenotypes defined by short DQα and DQβ cDNA probes correlate with and define splits of HLA-DQ serological specificities

Abstract

HLA-DR and -DQ serotyped cell lines and peripheral blood leucocytes were analysed by Southern blot allogenotyping. Using a short DQβ cDNA probe, a DQβ allelic series was defined by restriction fragment length polymorphism (RFLP) with the restriction endonuclease Taq I. This DQβ allelic series correlates with, and defines splits of, the HLA-DQ serological specificities DQw1 (DQβ1a and DQβ 1b RFLPs), DQw2 (DQβ2a and DQβ2b RFLPs) and DQw3 (DQβ3a and DQβ3b RFLPs). By sequential use of a short DQa cDNA probe a second, DQα allelic series is defined by RFLP. This series correlates to a lesser extent than DQβ RFLPs with the HLA-DQ serological specificities. Thus, two DQα RFLPs correlate with a single DQ serotype (DQα 1a and DQα 1c with DQw1), but three DQα RFLPs correlate with more than one DQ serotype (DQα1b with DQw1 and DQw3; DQα2 with DQw2 and DQw3; DQα3 with DQw2 and DQw3). Individual DQβ and DQα RFLP subtypes appear to correlate with single, or associated HLA-DR specificities. Specific combinations of DQβ with DQα RFLPs also correlate with HLA-Dw splits of DR2 and DRw6. A system for HLA-DNA typing is described, which uses RFLP patterns generated by sequential hybridization of TaqI-digested DNAs with short DRβ, DQβ and DQα cDNA probes. The DQβ and DQα probes not only identify the DQ allele, but because of linkage disequilibrium with DR, help to assign the DR allele, which may not always be identified with a DRβ probe alone.