Table 1: Possible explanations for some of the predominantly associated features in “AS.”

“AS” associated featuresSuggested explanation

Fluctuation in the course of the disease and low concordance rates in identical twinsInvolvement of nongenetic, environmental, factors in the disease pathogenesis

High association with HLA-B27
Cross-reactivity of these antigens with Klebsiella

Predilection for involvement of the sacroiliac and vertebral joints
Lymphatic drainage plexus of the bowel (containing Klebsiella antibodies) is in close proximity to the sacro-iliac joints

Polyarticular joint involvement

Cross-reactivity between collagen I, III, and IV fibres and Klebsiella

Associated uveitis
Cross-reactivity of uveal tract tissues with Klebsiella

Associated enthesitis
A site of inflammation in the early cases of AS

Increased total IgA and secretory IgA in sera of AS patientsEnhanced mucosal immune response due to subclinical bowel infections by Klebsiella

Higher onset of AS among young peopleIncreased intake of starch diet among young age groups