HLA-encoded genetic predisposition in IDDM: DR4 subtypes may be associated with different degrees of protection.
Recent studies have shown that the risk conferred by the high-risk DQA1*03-DQB1*0302 (DQ8) haplotype is modified by the DRB1*04 allele that is also carried by this haplotype. However, many of these studies suffer from lack of sufficient numbers of DQ-matched control subjects, which are necessary because there is a strong linkage disequilibrium between genes in the HLA complex. In the present study, using a large material of IDDM patients and DQ-matched control subjects, we have addressed the contribution of DR4 subtypes to IDDM susceptibility. Our data, together with recent data from others, clearly demonstrate that some DR4-DQ8 haplotypes are associated with disease susceptibility, while others are associated with protection, depending on the DRB1*04 allele carried by the same haplotype. In particular, our data demonstrate that DRB1*0401 confers a higher risk than DRB1*0404. Based on combined available data on the genetic susceptibility encoded by various DR4-DQ8 haplotypes and the amino acid composition of the involved DRbeta*04 chains as well as the ligand motifs for these DR4 subtypes, we have developed a unifying hypothesis explaining the different risks associated with different DR4-DQ8 haplotypes. We suggest that disease susceptibility is mainly conferred by DQ8 while DR4 subtypes confer different degrees of protection. Some DR4 subtypes (i.e., DRB1*0405, 0402, and 0401) confer little or no protection, while others (i.e., DRB1*0404, 0403, and 0406) cause an increasing degree of protection, possibly by binding a common protective peptide. Features of a protective peptide that fit such a model are briefly discussed.
Undlien
D E
DE
Institute of Transplantation Immunology, The National Hospital, Oslo, Norway. d.e.undlien@rh.uio.no
Friede
T
T
Rammensee
H G
HG
Joner
G
G
Dahl-Jørgensen
K
K
Søvik
O
O
Akselsen
H E
HE
Knutsen
I
I
Rønningen
K S
KS
Thorsby
E
E
D000293:Adolescent; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000235:genetics* / Q000276:immunology*; D004198:Disease Susceptibility; D005838:Genotype; D006683:HLA-DQ Antigens / Q000235:genetics*; D059848:HLA-DQ alpha-Chains; D006684:HLA-DR Antigens / Q000235:genetics*; D015804:HLA-DR4 Antigen / Q000235:genetics*; D059811:HLA-DRB1 Chains; D006239:Haplotypes; D006801:Humans; D012016:Reference Values; D018570:Risk Assessment; D012307:Risk Factors
D006683:HLA-DQ Antigens; D059848:HLA-DQ alpha-Chains; C069050:HLA-DQA1 antigen; D006684:HLA-DR Antigens; D015804:HLA-DR4 Antigen; D059811:HLA-DRB1 Chains; C553505:HLA-DRB1*04:01 antigen