IgA antibody response to klebsiella in ankylosing spondylitis measured by immunoblotting.

IgA antibodies to Klebsiella pneumoniae var oxytoca and Proteus mirabilis were measured in 66 patients with ankylosing spondylitis (AS) and 31 with rheumatoid arthritis (RA) and in 51 healthy control subjects, using an immunoblotting technique. The number of antigenic bands to klebsiella on nitrocellulose membrane was higher in 28 patients with active AS than in 38 patients with inactive AS, 31 patients with RA, and 51 healthy control subjects; comparatively smaller increases were found against proteus. In two patients with AS the synovial fluid and the corresponding serum sample showed an identical antibody pattern. Increases in IgA antibodies to klebsiella in patients with AS confirm previous studies using other techniques.