Serum IgA to enterobacteria in ankylosing spondylitis.

The aetiology of ankylosing spondylitis (AS) may involve certain enterobacteria. It is therefore interesting that serum polymeric IgA, a precursor of secretory IgA, was statistically elevated in active AS (n=35) and that levels were comparable to those found in yersiniosis (n=12); this might indicate antigenic stimulation by bacteria which are present in the intestines of AS patients. However, specific serum IgA to the incriminated enterobacteria Klebsiella, Shigella and Yersinia, as determined by ELISA, was not raised in the above AS patients. Nor were these litres raised in patients with idiopathic reactive arthritis (n=21). In contrast, yersiniosis (n=12) and shigellosis (n=96) patients displayed marked increases in specific serum IgA litres to the respective infectants. It is proposed that AS may involve a set of enterobacteria rather than a few suspected species. Thus, despite the lack of raised group averages, screening of individual patients for specific IgA to several indicated bacteria might disc...