DIVERSITY OF HLA-DR2 IN NORTH INDIANS - THE CHANGED SCENARIO AFTER THE DISCOVERY OF DRB1-ASTERISK-1506

DRB11506, a new allele of DR2, differs from DRB1*1501 only at codon 5 0 in the second exon, where the nucleotide sequence has changed from G TG to GCG resulting in an amino acid substitution from valine to alani ne in DRB11506. Since codon 50 was considered non-polymorphic until t he discovery of this new allele by sequence-based typing, it became ne cessary to study what fraction of subjects thought to have DRB11501 a ctually had DRB11506. For this purpose, 116 DNA samples with DR2 comi ng from normal healthy individuals, leprosy patients and childhood tub erculosis patients were amplified using PCR and hybridized with P-32-l abeled probes specific for DRB11501, DRB1*1502, DRB1*1503, DRB1*1506, DRB11601 and DRB1*1602. The oligonucleotide probe for DRB1*1506 was designed to span codons 47-52 based on the published nucleotide sequen ce. DRB5, DQA1 and DQB1-specific amplifications and hybridizations wer e also carried out to study the diversity of DR2 haplotypes. It was fo und that 21% of the samples identified previously as DRB11501 were ac tually DRB11506. DRB1*1506 was found to be associated with DQB1*0502 and DQB10601. Haplotypes of DRB1*1501, DRB1*1502, DRB1*1506 and DRB1* 1602 showed a marked heterogeneity. Besides the rare haplotypes which have not yet been reported in any other populations, haplotypes charac teristic of different ethnic groups, such as Croatians, South Chinese and Gypsies, were also found in the North Indians, suggesting the exte nt of racial admixture and migrations to and from India.