Ankylosing spondylitis, HLA-B27 and Klebsiella. II. Cross-reactivity studies with human tissue typing sera.

Human monospecific HLA B27 typing sera have been shown to have increased binding activity for klebsiella extracts by haemagglutination (P less than 0.001), radiobinding assay (P less than 0.025) and radiolabelled antigen competition assay (P less than 0.02) when compared to non-B27 tissue typing sera. These observations are in agreement with those of studies using rabbit sera, suggesting that HLA B27 lymphocytes may exhibit partial cross-reactivity with bacterial antigens found in some Gram-negative microorganisms such as klebsiella. It is suggested ankylosing spondylitis may occur as a result of immunological damage following infection by Gram-negative bacteria carrying antigens having stereochemical similarity to self antigens.