ABSTRACT
Early treatment of rheumatoid arthritis (RA) with disease-modifying antirheumatic drugs can achieve a better disease outcome and reduce the severity of joint damage. The presence of autoantibodies in patient sera can precede onset of the disease and thus be predictive of the development of RA. To date, known autoantibodies in RA are positive in only 50-60% of RA patients at onset of disease and even less before the onset of any RA symptom. The aim of this study was to identify new antibodies that could be useful for the diagnosis of RA using synovial membrane proteins, which represent the best source of candidate RA autoantigens. The humoral reactivity of sera from RA patients was explored using immunoblotting on extracted proteins obtained from synovial membranes from RA after synovectomy or arthroplasty. A new target protein with a molecular weight of 26 kDa was found to be recognized by autoantibodies in RA sera. This protein was identified using MALDI-TOF mass spectrometry and two-dimensional electrophoresis as carbonic anhydrase III with a high level of confidence. In conclusion, this study demonstrates new autoantibodies in RA patients that are directed against carbonic anhydrase III. The sensitivity and specificity of these new autoantibodies for RA have to be further evaluated.
Subject(s)
Arthritis, Rheumatoid/immunology , Autoantibodies/immunology , Autoantigens/immunology , Autoantigens/isolation & purification , Synovial Membrane/immunology , Arthritis, Rheumatoid/blood , Arthritis, Rheumatoid/diagnosis , Autoantibodies/blood , Blotting, Western , Carbonic Anhydrase III , Electrophoresis, Gel, Two-Dimensional , Electrophoresis, Polyacrylamide Gel , Humans , Spectrometry, Mass, Matrix-Assisted Laser Desorption-IonizationABSTRACT
The objective of this study was to identify new autoantibodies that could be useful for the diagnosis of rheumatoid arthritis (RA) using immunoblotting on synovial membrane proteins which represent the best source of candidate RA autoantigens. A new target protein with a molecular weight of 26 kDa was found to be recognized by autoantibodies in RA sera and was identified using MALDI-TOF mass spectrometry and second-dimension electrophoresis as carbonic anhydrase III (CAIII). Three similar protein spots at 26 kDa were recognized by both human sera and monoclonal antibody (mAb) directed against CAIII on immunoblotting using the human recombinant CAIII. Interestingly, CAIII expression within the synovial membrane was not observed in non-RA patients and was differentially expressed among RA patients. The sensitivity of these new autoantibodies for RA, using an immunoenzymatic technique, was 17%. Specificity was high when comparing non-autoimmune diseases (100%), while it was found to be weak (67%) when comparing some other autoimmune diseases, and particularly systemic lupus erythematosus (SLE). In conclusion, this study demonstrates that these new autoantibodies against CAIII are not restricted to RA. However the expression of CAIII in the synovial membrane of RA warrants further investigation of the pathophysiological relevance of this finding.
