The Role of Enterobacteriaceae in Ankylosing Spondylitis

McLellan, Susanne Marie (1990) The Role of Enterobacteriaceae in Ankylosing Spondylitis. PhD thesis, University of Glasgow.

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Abstract

In this study, we investigated the immune response of patients with Ankylosing Spondylitis (AS) and looked for evidence to support the proposal that AS is a form of reactive arthritis in which Klebsiella or other Enterobacteriaceae play a role. Immunoglobulin levels in patients' sera were measured. Using the laboratory parameters erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels as indicators of disease activity, it was found that patients with active disease had considerably higher levels of IgA and IgG than patients with inactive disease or controls. This suggests that these immunoglobulin levels could be another useful indicator of disease activity and they were therefore taken into account in all subsequent patient studies. It has been suggested that these high serum immunoglobulin levels indicate an ongoing immune response to antigen in patients with active disease, but such marked elevations are more likely to be accounted for by non-specific mechanisms. We had hoped to investigate any cellular basis for this by co-culturing AS and normal lymphocytes. However, in vitro immunoglobulin production by peripheral blood lymphocytes (PBLs) did not reflect the serum studies: we were unable to demonstrate any abnormality in the production of immunoglobulin by patients' lymphocytes. The possibility of involvement of Enterobacteriaceae in AS was studied by measuring the levels of specific antibody in patients' sera to sonicated preparations of several bacteria. An enzyme-linked immunosorbent assay (ELISA) was used. When total antibodies were measured (i.e. all immunoglobulin classes), no differences were found between patients and controls. However, when antibodies of the IgA class only were studied, patients were found to have elevated antibody levels to Klebsiella and the three arthritogenic bacteria Salmonella, Shigella and Yersinia. This was not simply a result of the general elevation in serum IgA found in patients since normal levels of IgA antibodies to E. coli and Proteus were found. Using SDS-polyacrylamide gel electrophoresis (PAGE) and immunoblotting, an attempt was then made to identify any abnormality in the level of serum antibodies to individual Klebsiella proteins. No obvious difference was found in the blotting pattern of sera from controls, patients with inactive disease and patients with active disease. Since Klebsiella and the other bacteria implicated in AS are found in the gut, a study of the gut immune response should provide a better indication of whether antigenic stimulation by such bacteria has occurred. We studied patients' saliva, the only gastrointestinal secretion readily available. In an ELISA, neither patients as a whole nor the active disease group had high levels of total salivary IgA or IgA antibodies to formalin-killed or sonicated Klebsiella or Yersinia. If, as it has been suggested, the immune response to Enterobacteriaceae plays a pathogenic role in the disease, we would expect to find evidence for this immune response at the site of inflammation - the joints. We measured antibodies to sonicated and formalin-killed preparations of Klebsiella, Salmonella, Shigella and Yersinia in synovial fluids. These antibody levels were no higher in AS patients than in patients with Rheumatoid Arthritis or other inflammatory joint diseases. Moreover, the antibody response to these four bacteria was similar to that found to E. coli, a bacterium which has not been implicated in the seronegative spondyloarthropathies. Further studies using immunoblotting revealed no difference between AS and other patients in the level of synovial fluid antibodies to individual Klebsiella proteins . In the known reactive arthritides, lymphocytes from the joint demonstrate an elevated cellular immune response to the causative organism. We therefore measured the in vitro proliferative response to Klebsiella of AS synovial T-cells. This was not significantly different from the response of synovial lymphocytes from patients with other diseases. The humoral immune response in AS was further studied by measuring the levels of circulating immune complexes (CIC) in patients' sera. Using a Raji assay, patients were found to have elevated levels of IgG-CIC which were associated with active disease while an assay based on polyethylene glycol (PEG) precipitation and radial immunodiffusion revealed a difference between patients and controls which was independent of disease avtivity. All patients had normal serum levels of IgM-CIC. Significant levels of both IgG- and IgM-immune complexes were found in AS synovial fluids. These immune complexes may have no pathogenic relevance but they could be useful in the identification of any environmental factors associated with the disease.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Immunology
Date of Award: 1990
Depositing User: Enlighten Team
Unique ID: glathesis:1990-78184
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:37
Last Modified: 30 Jan 2020 15:37
URI: http://theses.gla.ac.uk/id/eprint/78184

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