Objective. To measure antibodies to Klebsiella capsular polysaccharide
s in the sera of HLA-B27 positive patients with ankylosing spondylitis
(AS), compared with HLA-B27 positive and HLA-B27 negative healthy con
trol subjects. Methods. Antibodies were detected by means of an enzyme
-linked immunosorbent assay specific for each of the 77 known Klebsiel
la serotypes. Results. Significantly elevated frequencies and titers o
f antibodies to capsular polysaccharides K26, K36, and K50 were detect
ed in sera from AS patients, compared with controls. Conclusion. These
results suggest the predominance of Klebsiella serotypes K26, K36, an
d K50 in patients with AS.