Association of Major Histocompatibility Complex Class I Chain-Related Gene A and HLA-B Alleles with Behçet's Disease in Turkey.
OBJECTIVE
Behçet's disease (BD) is known to be associated with HLA-B*51 in many different ethnic groups. Recently, the major histocompatibility complex class I chain-related gene A (MICA), located near the HLA-B gene, has been proposed as a candidate gene for BD susceptibility in several ethnic groups. To compare the relative contribution of MICA polymorphisms and HLA-B*51 to BD in different ethnic groups, we studied MICA polymorphisms in Turkish BD patients.


METHODS
Thirty-three Turkish BD patients and 65 healthy controls were enrolled for analysis of polymorphisms in the extracellular domains of MICA.


RESULTS
The phenotype frequencies of MICA*009 were significantly higher in BD patients (75.8%) than in controls (29.2%) (P = 0.000015). HLA-B*51 was also significantly more frequent in BD patients (81.8%) than in controls (29.2%) (P = 0.0000007). A strong association existed between MICA*009 and HLA-B*51. To assess the confounding effect of MICA*009 on HLA-B*51, we performed a stratification analysis that showed that BD was distinctly associated only with HLA-B*51.


CONCLUSIONS
Our results indicate that the major susceptibility gene for BD is HLA-B*51 and that the association between MICA*009 and BD arises from a strong linkage disequilibrium with HLA-B*51. However, we suggest that MICA*009 likely elicits an immune effect secondary to BD.
D000483:Alleles; D001528:Behcet Syndrome / Q000208:ethnology / Q000235:genetics*; D015235:HLA-B Antigens / Q000235:genetics*; D059949:HLA-B51 Antigen; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006650:Histocompatibility Testing; D006801:Humans; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D014421:Turkey / Q000208:ethnology
D015235:HLA-B Antigens; D059949:HLA-B51 Antigen; D015395:Histocompatibility Antigens Class I; C099187:MHC class I-related chain A