Polymorphism of the transmembrane region of the MICA gene and human brucellosis.

We investigated the polymorphism of the transmembrane region of the MICA gene (major histocompatibility complex class I chain-related gene A) in relation to susceptibility to human brucellosis. We typed 114 patients with brucellosis and 121 healthy controls for MICA transmembrane polymorphism with polymerase chain reaction methods combined with fluorescent technology. We found a significant decrease in the frequency of the MICA-A4 allele in the patients with brucellosis compared with the controls (4.4% vs 10.3%, Pc = 0.03). The frequency of the MICA-A5 allele was increased in the group of patients with focal complications (15% vs 38%, Pc = 0.004). Our data suggest the MICA-A4 allele shows a tendency to be protective against infection by Brucella melitensis. Furthermore, the MICA-A5 allele appears to confer susceptibility to focal forms in patients with brucellosis.