Theoretical models to explain the association of HLA-B27 with ankylosing spondylitis

A critical examination of the five different models proposed to explain the "AS-B27" problem, has demonstrated, that two of these, the two-gene theory and the plasmid theory are no longer considered to provide satisfactory explanations of the phenomena. The remaining three theories are molecular mimicry, chemotaxis hypothesis and the receptor theory. It is difficult at this stage to decide which of these three models provides the best solution to the "AS-B27" problem, but a majority of research workers favour the receptor theory.

Rheumatoid arthritis and Proteus: a possible aetiological association

The presence of specific anti-Proteus antibodies in active, rheumatoid arthritis (RA) patients, has been demonstrated by four different techniques: indirect bacterial agglutination, ELISA, Western blotting and immunofluorescence. Furthermore, anti-HLA-DR4 tissue typing sera have been shown to bind to Proteus microorganisms, thereby suggesting some molecular similarity or cross-reactivity between bacteria and HLA antigens. The concept is proposed that Proteus-reactive arthritis occurs during active phases of RA and tissue damage is mediated through immunological activity involving HLA antigens.

The relationship between Klebsiella infection and ankylosing spondylitis

Ankylosing spondylitis (AS) is probably produced by repeated episodes of Klebsiella-reactive arthritis, usually in HLA-B27-positive individuals. This concept is based on immunological, microbiological and serological considerations. Immunological studies based on anti-B27 tissue typing sera and anti-B27 monoclonal antibodies indicate that HLA-B27 cross-reacts with antigens found in Klebsiella, Salmonella, Shigella and Yersinia micro-organisms. Salmonella, Shigella and Yersinia gut infections are associated with a reactive arthritis that occurs predominantly in HLA-B27-positive individuals. However, microbiological studies indicate that only Klebsiella, but not Salmonella, Shigella or Yersinia, can be isolated in faecal cultures obtained from AS patients. Furthermore, serological studies involving a number of different techniques demonstrate that only antibodies against Klebsiella, but not against Salmonella, Shigella or Yersinia, can be identified in active AS patients. The evidence is sufficiently extensive to warrant long-term studies involving Klebsiella reduction in the bowel flora of AS patients, in an attempt to reduce the severity and modify the development of the disease. It would appear that Klebsiella-reactive arthritis is the precursor stage occurring in the early and active phases of AS. Only future studies can determine whether this disease will remain a taxonomic curiosity or provide guidelines for therapeutic sequelae which will be of benefit to AS patients.

Antibodies to Klebsiella and Proteus microorganisms in ankylosing spondylitis and rheumatoid arthritis patients measured by ELISA

Antibodies to Klebsiella oxytoca and Proteus mirabilis in 21 active ankylosing spondylitis (AS), 13 active rheumatoid arthritis (RA), 19 inactive RA patients and 18 healthy controls were measured using enzyme-linked immunosorbent assay (ELISA). Elevated anti-Klebsiella antibodies were demonstrated in active AS patients compared to active RA (p less than 0.01), inactive RA patients (p less than 0.001) and controls (p less than 0.005). When measuring antibodies to Proteus, active RA patients showed higher levels of antibodies compared to active AS patients (p less than 0.005) and healthy controls (p less than 0.05). Further investigations are required to assess the role of Klebsiella and Proteus microorganisms in AS and RA respectively.

Klebsiella antibodies in ankylosing spondylitis and Proteus antibodies in rheumatoid arthritis

Antibodies to Klebsiella, but not to other bacteria, have been shown to be present in patients with active ankylosing spondylitis (AS) by seven different techniques. Antibodies to Proteus, but not to E. coli or Klebsiella, have been shown to be present in patients with active rheumatoid arthritis (RA) by three different techniques. It is suggested AS and RA are forms of reactive arthritis, to Klebsiella and Proteus respectively, probably mediated by cross-reactivity to HLA antigens.

A study of antipolynucleotide antibodies, anti-Klebsiella (K30) antibodies and anti-DNA antibody idiotypes in ankylosing spondylitis

Recent studies have indicated that both ankylosing spondylitis and the anti-DNA antibodies found in systemic lupus erythematosus may be related to Klebsiella surface antigens. In order to explore these possible relationships further, the sera of 24 patients with ankylosing spondylitis (AS), and 20 controls, have been examined for binding to a wide range of antipolynucleotide antibodies, antibodies binding to the Klebsiella pneumoniae polysaccharide K30 and two DNA antibody idiotypes designated 16/6 and 134. We report that although 21% of the AS patients had IgG ssDNA antibodies it is evident that the aetiopathogenesis of this disease is not through the mechanism of autoantibodies or the common DNA antibody idiotypes tested.

Antibodies to proteus in rheumatoid arthritis

Antibodies to proteus species were measured in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS) and in healthy controls by a Coombs agglutination method. The titres to Proteus mirabilis were higher in 30 RA patients being treated with gold than in 24 patients with active AS (p less than 0.001), 28 patients with inactive AS (p less than 0.001), and 41 healthy control subjects (p less than 0.001). Control studies with Klebsiella pneumoniae var oxytoca showed high antibody titres only in active AS patients.

Spondyloarthritis, uveitis, HLA-B27 and Klebsiella

The association between HLA-B27 and ankylosing spondylitis could be explained by a "crosstolerance hypothesis". Experimental studies demonstrate immunological crossreactivity between HLA-B27 and antigens found in Gram-negative bacteria, such as Klebsiella. Clinical studies show that an increased frequency of patients with ankylosing spondylitis and uveitis have Klebsiella in their fecal cultures. Furthermore, antibodies to Klebsiella can be detected in such patients during active phases of the disease. It is suggested that anti-bacterial antibodies bind to cross-reacting self-antigens, activate the complement cascade and produce inflammation which eventually leads to the development of such chronic diseases as ankylosing spondylitis and uveitis.

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.

Circulating immune complexes in ankylosing spondylitis

Circulating immune complexes were determined in the sera of patients with ankylosing spondylitis using a polyethylene glycol precipitation laser nephelometer technique. Positive results were obtained in 52% of sera from patients with active disease, but only in 20% from those in inactive stages. The immunoglobulin/complement protein ratio differed from that seen in rheumatoid arthritis and in systemic lupus erythematosus, due to the relatively larger amounts of C3 and C4 present in the immune complexes. These findings indicate that circulating immune complexes in ankylosing spondylitis may not be of pathogenetic significance because of their degree of solubilization.

The cross-tolerance hypothesis, HLA-B27 and ankylosing spondylitis

The association of HLA-B27 with ankylosing spondylitis (AS) can be explained by a cross-tolerance hypothesis, which suggests that Gram-negative bacteria, such as Klebsiella, possess antigens which resemble HLA-B27. Experimental studies with human tissue-typing sera and rabbit anti-Klebsiella sera would appear to be compatible with this hypothesis. Clinical studies indicate that faecal Klebsiella can be isolated more readily from AS patients during active phases of the disease, when this is defined either clinically, with or without uveitis, or biochemically by elevation in ESR and C-reactive protein levels. The cross-tolerance hypothesis proposes that ankylosing spondylitis is a reactive arthritis following infection by Gram-negative bacteria and tissue damage is produced by antibacterial antibody binding to cross-reacting self-antigens.

[Ankylosing spondylarthritis, HLA B27 and the theory of crossed tolerance]

The association between HLA-B27 and ankylosing spondylitis could be explained by a theory of crossed tolerance, which proposes that Gram negative bacteria have antigens similar to HLA-B27. Experimental studies with human sera with anti-HLA specificity and rabbit sera with anti-Klebsiella specificity demonstrate a partial crossed reactivity between HLA-B27 and Klebsiella. Clinical studies have shown that Klebsiella can be isolated from patients with ankylosing spondylitis during relapses or active phases of the disease. The theory of crossed tolerance proposes that ankylosing spondylitis is a reactive arthritis which develops after infection with Gram negative bacteria. The agent directly involved in causing the disease is an anti-bacterial antibody which binds to self antigens with partial crossed reactivity, such as HLA-B27, and the inflammation develops as a result of triggering of the complement cascade by the antigen-antibody complex.

Muscle changes in ankylosing spondylitis

Muscle biopsy of the quadriceps femoris was carried out in 20 patients with classical ankylosing spondylitis (AS). Histological and histochemical studies revealed changes in all biopsies to a varying degree. Central migration of nuclei was present in 80%, reduced fibre size with some atrophy in 40%, localized reaction to acid phosphatase in 75% and a peripheral condensation of reaction product to NADH-TR stain in 55% of biopsies. Furthermore 14 out of 16 patients, whose quadriceps strength was measured, were found to be below the predicted values, when compared to healthy controls of similar weight, and quantitative surface electromyography in 10 showed lower mean power frequency than in controls. A raised plasma creatine kinase was found in only two patients. It is concluded that muscle changes occur in AS and these may account for some of the clinical features of the disease.

IgA antibodies to Klebsiella pneumoniae in ankylosing spondylitis

Serum IgA antibodies to Klebsiella pneumoniae were measured in 65 patients with ankylosing spondylitis (AS) during different phases of disease activity and compared with the antibody level in 21 psoriatic arthritis (PsA) patients, 43 rheumatoid arthritis (RA) patients and 57 healthy controls. The mean IgA antibody to Klebsiella in AS patients with an erythrocyte sedimentation rate (ESR) greater than or equal to 15 mm/h was significantly higher than the antibody level in patients with an ESR less than 15 mm/h (p less than 0.02) and tended to increase with rising ESR. There was a significant difference in anti-Klebsiella antibody levels between AS patients with an elevated ESR and antibody levels in PsA patients (p less than 0.001), RA patients (p less than 0.001) and healthy controls (p less than 0.005). There was no difference between healthy controls and patients with PsA, RA or AS patients with a low ESR. The IgA anti-Klebsiella antibody was specifically absorbed out from sera with inactivated klebsiella pneumoniae organisms. Antibody levels to Candida albicans and Escherichia coli did not differ in patients vis-à-vis control subjects. The mean serum anti-Klebsiella IgA level was found to be higher in patients who were either clinically active or had positive faeval cultures, when compared with patients with inactive disease and negative cultures, but these differences were not statistically significant, although when both parameters were examined together a significant additive effect was detected (p less than 0.001). It is concluded that patient with AS exhibit a specific elevation of serum IgA antibody to Klebsiella antigen.

An investigation into the properties of klebsiella strains isolated from ankylosing spondylitis patients

Thirty-nine strains of klebsiella isolated from ankylosing spondylitis patients were examined by the methods of Cowan & Steel (1974), those described by Edmondson et al. (1980) and by capsular typing. No significant difference was detected by any of these methods between these strains and those examined by other workers from non-ankylosing spondylitis patients and other environments.

Yersinia enterocolitica biotype I. Diarrhoea and episodes of HLA B27 related ocular and rheumatic inflammatory disease in South-East England

Yersinia enterocolitica biotype I were isolated from faeces of 16% of 56 consecutive patients with diarrhoea or gastrointestinal symptoms and 2.8% of 109 healthy controls (p less than 0.01). Similar Yersinia biotypes were isolated from 4% of samples from 86 rheumatoid arthritis patients and 4.5% of samples from 140 ankylosing spondylitis patients examined regularly over an 8-month period. These results suggest that Yersinia enterocolitica biotype I are regular but infrequent inhabitants of the human gastrointestinal tract in south-east England. The increased isolation rate of these microorganisms from patients with enteric disease and from patients with exacerbations of HLA B27-related arthritic and ocular inflammatory disease justifies further investigations.

Uveitis, vitreous humour, and klebsiella. II. Cross-reactivity studies with radioimmunoassay

Radioimmunoassay with calf and cow vitreous humour-I125 and rabbit antivitreous humour serum has been employed to investigate the immunological cross-reactivity of vitreous humour with bacterial and mammalian tissue antigens. Klebsiella ultrasonicate preparation at a dose fo 10 000 micrograms/ml was found to inhibit the binding of vitreous humour by 25-100% (p less than 0.001), compared with an inhibition of 5-30% by a similar quantity of E. coli ultrasonicate preparation. Equivalent amounts of Streptococcus pyogenes antigen, bovine haemoglobin, and hyaluronic acid had no inhibitory effect, while horse spleen ferritin was found to inhibit vitreous humour binding between 0 and 10%. These results indicate that klebsiella micro-organisms have antigens which partially resemble some eyeball components. It is suggested that acute anterior uveitis of ankylosing spondylitis may be produced by anti-Gram-negative bacterial antibodies binding to cross-reacting eye antigens.