HLA-B27 and the immune response to enterobacterial antigens in ankylosing spondylitis

Total serum immunoglobulins and class specific serum antibodies to Klebsiella pneumoniae, Salmonella typhimurium, Yersinia enterocolitica and Pseudomonas aeruginosa were measured in 107 patients with ankylosing spondylitis (AS) and 110 healthy tissue typed controls by enzyme linked immunosorbent assay (ELISA). The specificity of this technique was confirmed by the use of specific bacterial murine antisera and by cross-absorption of human sera by specific bacteria. Total serum IgA in AS patients correlated with both erythrocyte sedimentation rate (ESR) (P less than 0.001) and C-reactive protein (P less than 0.05) and was significantly elevated compared to healthy individuals (P less than 0.001). A significant elevation of IgA antibodies to K. pneumoniae was detected in the serum of AS patients with active disease when compared to healthy controls (P less than 0.01). These studies support the involvement of an enterobacterial micro-organism in the pathogenesis of AS and further relate to the role of HLA-B27 in this disease.