HLA-DRB4 Gene Encoded HLA-DR53 Specificity Segregating with the HLA-DR7, -DQ9 Haplotype: Unusual Association

HLA phenotyping of a leukemia patient of Caucasoid origin revealed the presence of the serological HLA-DR53 specificity. Comprehensive pedigree analysis demonstrated that the HLA-DR53 specificity segregated with the HLA-DR7, -DQ3 haplotype. High resolution PCR- SSP genotyping of the HLA class II genes revealed the presence of the HLA-DRB4∗0101101 allele segregating together with the HLA-DRB1∗0701, -DQA1∗0201 and DQB1∗03032 alleles. This finding is in contrast to known linkages in that thus far, the HLA-DR7, -DQ9 haplotype has only been described in association with the non-expressed HLA-DRB4∗0103102N allele. The existence of this “novel” haplotype may be explained by a homologous recombinational event that occured between the HLA-DR7, -DR53, -DQ2 and the HLA-DR7, -DQ9 haplotypes.