Immune functions and inflammatory reactions in HLA-B27 positive subjects.

The association between the major histocompatibility antigen HLA-B27 and ankylosing spondylitis is the strongest of all known associations between class I HLA and disease. Over 90% of patients with ankylosing spondylitis have B27,1 whereas it is found only in 7-15% of normal white subjects. In addition, B27 is associated with certain reactive inflammatory conditions following gastrointestinal or urogenital infections. For example, about 80% of patients with reactive arthritis triggered by Yersinia enterocolitica or Yersinia pseudotuberculosis are B27 positive.2 Complete Reiter's syndrome, sacroiliitis, and acute anterior uveitis also belong to the same group of diseases.4 The collective term spondyloarthropathy is used for these diseases. It is commonly supposed that similar pathogenic mechanisms contribute to the development of all B27 associated diseases. An excess of B27 has also been described in psoriatic arthritis,5 in disorders of cardiac conduction,6 the latter reflecting the role of ankylosing spondylitis, in schizophrenia,7 and even in classical rheumatoid arthritis.8