IgA1 and IgA2 subclass antibodies against Klebsiella pneumoniae in the sera of patients with peripheral and axial types of ankylosing spondylitis.

OBJECTIVE To study further the Klebsiella specific serum antibody response in patients with axial and peripheral types of ankylosing spondylitis (AS). METHODS IgA1 and IgA2 subclass antibodies to Klebsiella pneumoniae were measured by enzyme linked immunosorbent assay in the sera of 171 patients with axial or peripheral type AS, and in sera of 100 healthy controls. The effect of 26 weeks of sulphasalazine treatment on the antibody levels in the two types of AS was also analysed. RESULTS K pneumoniae specific antibody levels of both IgA1 and IgA2 subclasses were increased in the sera of patients with AS compared with healthy controls. The increased levels were present in patients with axial and with peripheral AS, and there were no statistically significant differences in the antibody levels between these two groups. Sulphasalazine treatment decreased the Klebsiella specific antibody level of IgA1 subclass in patients with axial AS, but there were no statistically significant changes in the IgA2 subclass, or in the patients with peripheral type AS. CONCLUSIONS These results agree with earlier published findings suggesting that IgA (especially Klebsiella specific IgA) may have a role in the pathogenetic mechanisms of both peripheral and axial types of AS. In addition, it seems that both IgA1 and IgA2 subclasses are involved in the disease process.