Serum IgA anti-Klebsiella antibodies in ankylosing spondylitis patients from Catalonia.

IgA antibodies against Klebsiella pneumoniae were measured by immunofluorescence in 84 Catalan patients with ankylosing spondylitis (AS), 41 patients with non-inflammatory arthropathies (NIA) and 22 patients with rheumatoid arthritis (RA). Patients with AS showed higher levels of anti-klebsiella IgA antibodies (IgA-Kp) than NIA and RA patients (4.7 +/- 1.6 U vs 3.7 +/- 1.5 U and 3.1 +/- 1.4 U respectively, p = 0.001). In AS patients a significant correlation between IgA-Kp and levels of C-reactive protein was observed. Although no clear correlation was found between IgA anti-klebsiella and total serum IgA levels, a significant correlation between IgA anti-klebsiella and serum levels of secretory IgA was detected (r: 0.43, p = 0.003). In conclusion, some patients with AS disclosed raised levels of Klebsiella antibodies in sera and this is related to an increase of secretory IgA level. Analysis about the relationship between response to klebsiella and the presence of gut inflammation in AS patients could be of interest.