IgA class serum antibodies against three different Klebsiella serotypes in ankylosing spondylitis.

OBJECTIVE To investigate the possible predominance of certain Klebsiella pneumoniae capsular types in the pathogenesis of ankylosing spondylitis (AS). METHODS The prevalence of IgA class antibodies against three different K. pneumoniae strains (with capsular types 21, 30 and 43) was studied in the sera of 177 patients with AS and of 100 healthy blood donors using an enzyme-linked immunosorbent assay. RESULTS The median Klebsiella-specific antibody levels were always higher in patients than in controls regardless of the serotype used as antigen. When the prevalence of increased antibody levels was compared between the groups, it was highest against the strain with capsular type 30, whereas against strains 21 and 43 it was similar among patients and controls. CONCLUSIONS A broad range of Klebsiella serotypes may be involved in the pathogenesis of AS. Thus, it is important to take the different Klebsiella serotypes into particular account in these studies.