158-P

Abstract

Aim We recently identified a patient carrying an HLA DR4 allele without having any allele of the DR53-expressed group or the common null allele DRB4∗01:03NDR53. The type was obtained using our routine typing method of SSP with Invitrogen reagents and software. It was then confirmed using the Olerup SSP typing tray and software. We then referred the specimen to the HLA laboratory at Stanford University, where the typing was repeated using several SSOP and SSP tests with a variety of reagents. The compound interpretation of all tests showed the DRB genotype would be DRB1∗13:01, DRB1∗04:01, DRB3∗01:01, DRB4∗03:01N. The allele DRB4∗03:01N lacks exon-2(full deletion)of DRB and carries an intact exon-3. This gene does not encode any functional histocompatibility antigen. The finding intriguing in itself since DRB4∗03:01N has been described previously in a haplotype carrying DRB1∗07:01-DRB4∗03:01N-DQB1∗02:02. In this case, the haplotype has DRB1∗04:01. Therefore this is a new independent mechanism for the generation of DRB4∗03:01N. It is not surprising since it is only the loss of an exon. We do not have all the details that both alleles would be the same since intron sequencing would be required to show similarities or differences. Methods SSP and SSOP typing. Results See body of abstract. Conclusions The case illustrates the point that DR53 needs to be typed for and not assumed because of the presence of DR4.