Association of MICA alleles and HLA-B51 in Italian patients with Behcet's disease

Objective. To evaluate the distribution of the MHC class I chain related ge ne A transmembrane (MICA-TM) alleles in Italian patients with Behcet's dise ase (BD), and to investigate the relative contribution of MICA alleles and HLA-B51 in the susceptibility and specific clinical features of BD. Methods. A total of 69 consecutive Italian patients who satisfied the Inter national Study Group criteria for BD were followed at rheumatology, ophthal mology, and neurology units during a 3 year period (1997-99). We selected 1 30 healthy subjects from the same geographic areas as controls. All patient s and controls were examined for MICA microsatellite polymorphisms using po lymerase chain reaction. Serological HLA class B51 typing was performed by a standard microlymphocyto-toxicity technique. Results. A strong association with HLA-B51 was observed in patients with BD (OR 5.7, 95% CI 2.8-11.3). The MICA-TM allele A6, in linkage disequilibriu m with HLA-B51, was only slightly increased in patients compared to control s (60.9% vs 50.8%; p = NS). No significant associations between HLA-B51 or MICA-TM alleles and clinical subgroups, particularly central nervous system or eye involvement, were found. Conclusion. HLA-B51 is the most important susceptibility gene in BD. Associ ation with MICA-A6, when it exists, is secondary to the strong linkage dise quilibrium with HLA-B51.