The role of Klebsiella in the pathogenesis of ankylosing spondylitis. II Evidence for a specific B27-associated marker on the lymphocytes of patients with ankylosing spondylitis.

Although the strong association of HLA-B27 with ankylosing spondylitis (AS) is well documented, the significance of this association is largely unknown. It has recently been reported that Klebsiella pneumoniae was present in the faeces of patients with AS more frequently than in healthy individuals, and that there appeared to be some cross-reactivity between HLA-B27 and Klebsiella. We have therefore attempted to gain an insight into the possible role of Klebsiella in the pathogenesis of AS. The results presented here indicate that HLA-B27 positive individuals with AS have a significantly lower in vitro lymphocyte responsiveness to Klebsiella antigens, as compared with B27 positive and B27 negative healthy controls. By contrast, B27 positive patients with AS as well as B27 positive and negative controls respond equally well to phytohaemagglutinin, Staphylococcus, Streptococcus, Yersinia and Shigella. To investigate a possible cross-reactivity between Klebsiella and HLA-B27, antisera were raised in rabbits against various isolates of Klebsiella. An antiserum to one isolate (427) of Klebsiella lysed the lymphocytes of B27 positive AS patients but not of B27 positive or B27 negative controls. These observations strongly suggest that some Klebsiella antigens cross-react with a gene product closely associated with HLA-B27 or possibly with a modified B27 antigen in patients with AS.