New HLA‐D Alleles Associated with DRI and DR2

The present study describes two new HLA‐D specificities: LD13, associated with DR1, and LD14 associated with DR2. LD13 is defined by an HTC who is the bc offspring of an a: A25, B18, DR7, Dw7/b: A33, B14, DR1, Dx father, and of a c: A24, B14, DR1, Dx/d: A26, B41, DR5, Dw5 mother. This HTC was included both as a responder and as a stimulator in our cross‐reference studies of 8W HTCs. While failing to cluster with any other 8W HTC, it typed 2 of 64 panel members carrying a “blank” HLA‐D, linked to DR1. To exclude the possibility that HTC‐LD13 might be a split of Dw1, the entire family was tested with the Family Set of 8W HTCs. No typing responses to any 8W Dw1 HTCs were observed. Furthermore, checkerboard experiments between HTC‐LD 13 and 8W Dw1 HTCs showed strong reciprocal stimulation. The LD13 specificity was only found in Ashkenazi Jews and may be in linkage disequilibrium with HLA‐B14. LD14 is defined by three, SD different, HTCs deriving from the same family of Sicilian descent. The family was included in the 8th Workshop and each HTC was shown to have inherited DR2, MT1 from both parents. When tested as stimulators, on our HLA‐D reference panel, these cells were clustered in a distinct group, LD14, associated with DR2. None of the 8W HTCs appeared to belong to this cluster. The antigen frequency of LD14 is 0.03.