Objective: To investigate the association between the exons 2 to 4 of the MICA gene and ankylosing spondylitis (AS).
Methods: By PCR-SSOP, DNA samples from 56 AS patients and 112 random healthy individuals, as normal control were genotyped to analyse the polymorphism in exons 2, 3, 4 of the MICA alleles.
Results: MICA*008 was dominant in MICA allele,accounted for 32.14% and 30.36% in AS patients and normal controls respectively. The frequency of MICA*007 was significantly increased in AS patients, when compared with normal controls (chi-square=10.18, P<0.05, RR=2.50). No difference was found in the other MICA alleles. The haplotype analysis revealed that there were the strong linkage disequilibrium between MICA and HLA-B of AS patients, and normal controls. There was a difference in MICA*007-B27 between two groups (chi-square=18.46, P<0.05, RR=7.47). Both HLA-B27 and MICA*007 were strongly associated with AS. Stratified analysis showed that HLA-B27 was significantly relative to AS,while it was not found between MICA*007 and AS.
Conclusion: The increased frequency of MICA alleles may be due to its strong linkage disequilibrium with HLA-B27.