A DELETION IN THE 2ND EXON OF AN HLA-DRB1 ALLELE FOUND IN A DR2-NEGATIVE NARCOLEPSY PATIENT

In this report, we describe a new allele of the HLA-DRB 1 gene carryin g a form of mutation that has not been observed before. It appeared in an HLA-DR2-negative narcolepsy patient who, besides HLA-DR4, revealed a serologic HLA-DR blank segregating with HLA-DQ1. Oligotyping showed that the new allele belongs to the HLA-DR8 group. Restriction analysi s and DNA sequencing revealed the deletion of 12 bp as well as the sub stitution of 9 flanking base pairs between codons 36 and 43. The expre ssion of the mutated gene was demonstrated by the presence of its mess enger RNA and a few positive reactions with DR8 sera. Without interrup ting the reading frame, the mutation leads to a gene product composed of a modified amino acid sequence. We anticipate that the mutation inf luences the conformation of the molecule with possible consequences co ncerning immune response.