Definition of LD "4 X 7": a unique HLA-D specificity defined by two homozygous typing cells.

Two homozygous typing cells (HTC) from the Eighth International Histocompatibility Workshop were used to define a unique HLA-D specificity, designated LD "4 X 7". Typing cell 8W316 (Seattle) was obtained from a donor of Japanese descent; cell 8W324 (Leiden) was obtained from a European Caucasian donor. The HLA-D specificities defined by these two HTC showed a significant correlation (R = 0.65) in unselected panel studies and clear segregation as a single determinant within families. LD "4 X 7" was found in low frequency in Caucasians (1.0%) but with detected with a frequency of 24% in Japanese. The cells of the donors of HTC 8W316 and 8W324 express DRw9, and the LD "4 X 7" antigen fills an HLA-D locus "blank" on DRw9-positive haplotypes. The frequency of LD "4 X 7" noted in this study corresponds to the frequency of DRw9 reported for Japanese and Caucasian ethnic groups, a further indication that LD "4 X 7" and DRw9 are associated.