Spondyloarthritis, uveitis, HLA-B27 and Klebsiella.

The association between HLA-B27 and ankylosing spondylitis could be explained by a "crosstolerance hypothesis". Experimental studies demonstrate immunological crossreactivity between HLA-B27 and antigens found in Gram-negative bacteria, such as Klebsiella. Clinical studies show that an increased frequency of patients with ankylosing spondylitis and uveitis have Klebsiella in their fecal cultures. Furthermore, antibodies to Klebsiella can be detected in such patients during active phases of the disease. It is suggested that anti-bacterial antibodies bind to cross-reacting self-antigens, activate the complement cascade and produce inflammation which eventually leads to the development of such chronic diseases as ankylosing spondylitis and uveitis.