Polymorphism in the regulatory region of HLA-DRB genes correlating with haplotype evolution.

Class II genes of the human major histocompatibility complex (MHC) are polymorphic. Allelic variation of the coding region of these genes is involved in the antigen presentation and is associated with susceptibility to certain autoimmune diseases. The DR region is unique among human class II regions in that multiple DRB genes are expressed. Differential expression of the different DRB loci has been demonstrated, and we sequenced the proximal promoter region of the HLA-DRB genes, known to be involved in the regulation of these genes. We found locus-specific and allele-specific nucleotide variations in their regulatory regions and we determined the relationship between the regulatory regions of HLA-DRB genes. This polymorphism found in the regulatory conserved boxes could be involved in the observed differential expression of DRB loci. In addition, we found a polymorphism between the regulatory regions of DRB1 alleles which might be involved in an allele-specific regulation and therefore could be considered as an additional factor in susceptibility to autoimmune diseases.