MICA and Behcet disease: The appearance of BD lesions is not directly correlated with HLA-B51 in the immunological background of the patients, but it was recently found that HLA-B51-restricted cytotoxic T lymphocytes (CTLs) and γδT cells played some roles in correlation with the stressed target tissues expressing major histocompatibility complex class I-related gene A (MICA) in BD pathogenesis.