Rheumatoid factors and amyloidosis in rheumatoid arthritis

Tumor necrosis factor alpha, its soluble receptor I, and -308 gene promoter polymorphism in patients with rheumatoid arthritis with or without amyloidosis: implications for the pathogenesis of nephropathy and anemia of chronic disease in reactive amyloidosis

OBJECTIVE

To study tumor necrosis factor alpha (TNFalpha) -308 gene promoter polymorphism and circulating levels of TNFalpha and soluble TNF receptor type I (sTNFRI) in rheumatoid arthritis (RA) patients with and without reactive amyloidosis.

METHODS

In a retrospective study, we examined 55 RA patients with biopsy-proven reactive amyloidosis and 55 control RA patients without amyloidosis (matched for age, sex, rheumatoid factor titer, and RA duration). Inflammatory activity was assessed by measuring the erythrocyte sedimentation rate and C-reactive protein level. TNFalpha gene promoter polymorphism was studied using polymerase chain reaction-restriction fragment length polymorphism assay. Cytokine and receptor levels were measured by enzyme-linked immunoassays.

RESULTS

Patients with RA and amyloidosis had significantly higher TNFalpha and sTNFRI levels than did the control RA patients. The increased circulating levels of TNFalpha correlated with interleukin-18 levels, but not with the serum amyloid A protein levels or with TNFalpha -308 gene promoter polymorphism (reported to be associated with high TNFalpha levels and certain disease susceptibilities). In the patients with RA and amyloidosis, those with anemia had significantly higher TNFalpha and sTNFRI levels than did those without anemia, and circulating TNFalpha and sTNFRI levels correlated negatively with hemoglobin concentrations. In the patients with RA and amyloidosis, those with nephropathy had significantly higher TNFalpha and sTNFRI levels than did those without nephropathy; in patients with isolated proteinuria (but no creatinine elevation) the TNFalpha level was also significantly increased, indicating that the TNFalpha elevation was not merely a consequence of impaired renal function.

CONCLUSION

This study shows that circulating levels of TNFalpha and sTNFRI are significantly increased in RA patients with amyloidosis as compared with control RA patients without amyloidosis and that the increased levels may be implicated in the pathogenesis of certain disease manifestations, including anemia of chronic disease and renal pathology in reactive amyloidosis.

Screening for amyloid in subcutaneous fat tissue of Egyptian patients with rheumatoid arthritis: clinical and laboratory characteristics

OBJECTIVE

To screen for amyloid and to assess associated clinical and laboratory characteristics in Egyptian patients with rheumatoid arthritis (RA).

METHODS

Abdominal subcutaneous fat aspirates were consecutively collected from 112 patients (103 women, nine men) having RA for five years or more. To detect amyloid, fat smears were stained with Congo red and the concentration of amyloid A protein in fat tissue was measured. Clinical, radiological, and laboratory characteristics of the patients were assessed.

RESULTS

Amyloid was detected in eight (7%) of the fat smears stained with Congo red. Compared with the Congo red stain, the sensitivity for detecting amyloid by measurement of amyloid A protein in fat tissue was 75% and the specificity was 100%. The amount of amyloid found was small for both methods. The median disease duration of the eight amyloid patients was significantly longer (17 years) than that of the non-amyloid patients (10 years). Bronchopulmonary disease and constipation were more common, whereas proteinuria and chronic renal insufficiency were not. The number of swollen joints and the number of red blood cells were significantly lower in the amyloid group.

CONCLUSIONS

Quantification of amyloid A protein and staining with Congo red are strongly concordant methods of screening for amyloid in fat tissue. The prevalence of amyloid in Egyptian patients with RA is 7%. Proteinuria is not a discriminating feature, whereas long disease duration, constipation, bronchopulmonary symptoms, and a moderate to low number of red blood cells may help to identify the arthritic patients with amyloid.

HLA typing and seropositivity in Finnish and in Polish patients with rheumatoid arthritis and amyloidosis

We determined HLA-A, -B, -C and -DR antigens in 83 patients with rheumatoid arthritis (RA) and reactive secondary amyloidosis (RSA), 60 in Finland and 23 in Poland, and compared the results with control RA patients and blood donors. There were no significant differences in the frequencies of HLA between the RA patients with and those without RSA in either Finland or Poland, and no significant differences between the Finnish and Polish patients with RSA. All the RSA patients from Finland and 70% of the RSA patients from Poland were seropositive. In the development of RSA, the prolonged period of inflammatory stimuli may play a more important role than genetic factors.

Antibodies to amyloid A protein in rheumatic diseases

Circulating autoantibodies against amyloid A protein (AA) were demonstrated by enzyme immunoassay in 18/62 patients with rheumatoid arthritis (RA) and in 9/27 patients with systemic lupus erythematosus (SLE). In the subset of RA patients who had developed amyloid, the frequency of antibodies to AA was lower than in those without amyloid (P less than 0.05). The antibody levels showed some variation in serial serum samples during follow-up (1-4 years) of patients with amyloidosis or SLE, but did not correlate with disease activity. In contrast to the patients with rheumatic diseases, patients with inflammatory bowel disease and acute bacterial peritonitis had antibody levels within the range of the healthy control subjects. The results show that autoantibodies to protein AA may occur in rheumatic diseases; their occurrence does not, however, identify subjects with tissue amyloid deposits. Absorption experiments suggest that the antibodies may be directed to circulating amyloid A protein.

Renal biochemistry in rheumatic disease

In patients with osteo-arthritis, renal disease will almost invariably be the consequence of unrelated coincidental renal pathology. In polyarthritic rheumatoid arthritis and ankylosing spondylitis, renal disease can arise as part of the pathology of a systemic disease, or more likely its treatment. As a rule amyloidosis is the most important complication in terms of progressive irreversible loss of renal function. By contrast, SLE, polyarteritis and Sjögren's disease carry a much higher risk of renal involvement. The regular evaluation of renal function in such patients can enable the kidney damage to be assessed at an early stage and allow treatment to be instituted early.

Amyloidosis

Recent studies have provided new insight into the pathogenesis of amyloidosis and have broadened our knowledge of the mechanisms of deposition and resolution of amyloid. In particular, the structure, synthesis and plasma clearance of the inflammation-associated amyloid precursor, SAA, have been extensively studied and the precursor-product relationship between circulating SAA, protein AA and fibrillar amyloid A clarified. Information has been accumulating about the enzymatic processes involved in the cleavage of SAA and the degradation of protein AA and a new view has been presented on the possible role of amyloid P component in AA amyloidogenesis. The current model of AA pathogenesis emphasizes the dynamic character of amyloid.

Rheumatoid factor in rheumatoid arthritis associated renal disease and in lupus nephritis

To test the hypothesis that rheumatoid factor (RF) protects against (immune complex mediated) renal disease, patients with rheumatoid arthritis (RA; 48 with nephropathy of various types, 35 without renal disease) and systemic lupus erythematosus (SLE; 35 with and 17 without nephritis) were evaluated for the presence and titre of RF. There was no correlation between RF and nephropathy in RA, whereas in SLE RFs were almost exclusively seen in patients without nephropathy. This result supports the above hypothesis for lupus nephropathy but not for RA associated renal disease, and it may be explained by a more pronounced role for immune complexes in SLE and interference of RFs with the complexes.

Enzyme immunoassay of complement-binding rheumatoid factors

We describe an enzyme immunoassay for the determination of complement-binding rheumatoid factors. Polystyrene tubes are coated with heat aggregated human IgG. The rheumatoid factors (RFs) of patients heat inactivated sera are allowed to bind to aggregated IgG and thereafter saturated with fresh human complement. The amount of C3 complement bound is measured by indirect enzyme immunoassay. The levels of complement binding RFs were measured in 30 patients with seropositive rheumatoid arthritis (RA), in 19 patients with systemic lupus erythematosus (SLE), and in 30 healthy control subjects. Compared to the controls high levels of complement-binding RFs were found both in RA and in SLE (P less than 0.0005). The mean level of the complement binding RFs was higher (P less than 0.05) in active than in inactive SLE. Even though the 19 S IgM RF bound complement, in RA no correlation was found between the level of complement binding RFs and Waaler-Rose titre, but the level of complement binding RF correlated with the levels of nonagglutinating IgM RF (r = 0.56, P less than 0.01) and IgG RF (r = 0.70, P less than 0.001) that were obtained by enzyme immunoassay.