IgA antibodies to Klebsiella pneumoniae in ankylosing spondylitis.

Serum IgA antibodies to Klebsiella pneumoniae were measured in 65 patients with ankylosing spondylitis (AS) during different phases of disease activity and compared with the antibody level in 21 psoriatic arthritis (PsA) patients, 43 rheumatoid arthritis (RA) patients and 57 healthy controls. The mean IgA antibody to Klebsiella in AS patients with an erythrocyte sedimentation rate (ESR) greater than or equal to 15 mm/h was significantly higher than the antibody level in patients with an ESR less than 15 mm/h (p less than 0.02) and tended to increase with rising ESR. There was a significant difference in anti-Klebsiella antibody levels between AS patients with an elevated ESR and antibody levels in PsA patients (p less than 0.001), RA patients (p less than 0.001) and healthy controls (p less than 0.005). There was no difference between healthy controls and patients with PsA, RA or AS patients with a low ESR. The IgA anti-Klebsiella antibody was specifically absorbed out from sera with inactivated klebsiella pneumoniae organisms. Antibody levels to Candida albicans and Escherichia coli did not differ in patients vis-à-vis control subjects. The mean serum anti-Klebsiella IgA level was found to be higher in patients who were either clinically active or had positive faeval cultures, when compared with patients with inactive disease and negative cultures, but these differences were not statistically significant, although when both parameters were examined together a significant additive effect was detected (p less than 0.001). It is concluded that patient with AS exhibit a specific elevation of serum IgA antibody to Klebsiella antigen.