Persistence of HLA-B27 cross-reactive bacteria in bowel flora of patients with ankylosing spondylitis.

Previous studies have shown that antisera raised in rabbits to certain enteric bacteria (cross-reactive bacteria) are capable of specifically lysing in a 51chromium-release lymphocytotoxicity test the lymphocytes of HLA-B27-positive (B27+) patients with ankylosing spondylitis (AS). This study investigated the clinical relevance of this finding by ascertaining whether Escherichia coli isolated from the rectal swabs of 20 B27+ AS patients (B27+ AS+) and 46 controls (35 B27- AS- and 11 B27+ AS-) were able to absorb the lymphocytotoxic activity of these antisera. All isolates from B27+ AS+ patients and one from a B27- AS- individual were capable of removing this activity. These organisms persisted in the bowel flora of five selected patients for at least 9 months. Cross-reactive bacteria were also found in a range of gram-positive organisms, including streptococcal, staphylococcal, and clostridial species. The relevance of these findings is discussed in terms of a pathogenetic concept relating the persistence of cross-reactive bacteria in the bowel flora of B27+ individuals to an early event in the development of AS.