Two sets of HLA Class II DRB and DQB1 alleles co-segregate among family members in a single maternal haplotype

HLA class II typing by sequence specific oligonucleotide probes (SSOP) on the family of a Burkit's Lymphoma patient produced hybridization patterns indicating the presence of two DRB1, and two linked DQB1 genes on the same maternal chromosome. DRB and DQB1 exon 2 amplification products associated with the novel maternal haplotype were identified by DNA typing techniques: These products corresponded to DRB1*0101, DRB1*1501, DRB5*01, DQB1*0501 and DQB1*0602 alleles. These alleles were seen to co-segregate among siblings sharing the same maternal haplotype. The patient, his mother and two of his siblings each appeared to possess elements of three DRB1, DQA1 and DQB1 genes. HLA DNA typing results indicated that a DNA sequence of approximately 100 Kb, spanning the region between, and including, DRB1 and DQB1 genes was inserted into the maternal haplotype. Serological typing on EBV transformed B lymphocytes obtained from the patient's mother showed three expressed DRB1 antigens. Serology on EBV transformed patient's cells also indicated multiple DRB1 antigen expression. The expression of three DRB1 and DQB1 genes on the cells of this patient would make it virtually impossible to obtain a suitably matched unrelated stem cell donor.