MICA GENE POLYMORPHISMS AND HLA-B27 SUBTYPES IN JAPANESE PATIENTS WITH HLA-B27-ASSOCIATED ACUTE ANTERIOR UVEITIS

PURPOSE. HLA-B27-associated acute anterior uveitis (HLA- B27 AAU) seem s to be triggered by external factors in persons with a particular gen etic background. It is still uncertain whether HLA-B27 or other gene(s ) near the HLA-B region predisposes to uveitis in a linkage disequilib rium with B27. The authors investigated microsatellite polymorphism wi thin the transmembrane region of the MICA gene, located 47 kb centrome ric of the HLA-B gene, and HLA-B27 subtypes. METHODS. Seventeen HLA-B2 7-positive Japanese patients with HLA-B27 AAU, 51 Japanese controls, a nd 20 B27-positive Japanese controls were examined for MICA gene polym orphism within the transmembrane region using polymerase chain reactio n (PCR) and subsequent automated fragment detection by fluorescent-bas ed technology. Furthermore. B27-positive patients with HLA-B27 AAU and B27-positive controls were examined for HLA-B27 subtypes by the PCR-s equence-specific primer method. RESULTS. The microsatellite allele in the MICA gene, consisting of four repetitions of GCT/AGC (designated A -4 allele), was present at a significantly higher phenotype frequency in the patient group (64.7%) than in the control group (25.5%) (chi(2) = 6.95, P-c = 0.042). Furthermore, the frequency of the A4 allele was significantly higher, even when compared with 20% in the B27-positive control group (chi(2) = 5.88, P-c = 0.042). The frequency of HLA-B27 subtypes was not significantly different between B27-positive patients with HLA-B27 AAU and B27-positive controls. CONCLUSIONS. These result s suggest that the MICA gene itself, or other nearby gene(s), linked t o MICA A4 allele may be involved in the development of HLA-B27 AAU and that HLA-B27 subtypes are not important in the development of HLA-B27 AAU in a Japanese population.