Antibodies Against the CB10 Fragment of Type II Collagen
Antibodies against intact type II collagen (CII) are a feature of rheumatoid arthritis (RA) but have limited diagnostic value. Here we assess whether either of the two major cyanogen bromide fragments of CII, namely CB10 or CB11, are more sensitive substrates for the detection of antibodies in RA. Cleavage of bovine CII with cyanogen bromide yielded CB10 and CB11; these were purified by column chromatography for use in an enzyme-linked immunosorbent assay. Serum antibodies were measured in patients with RA, psoriatic arthritis (PsA), osteoarthritis (OA) and blood donors. Results were compared with those using intact CII. Antibodies against CB10 were found in as many as 88% of 96 patients with long-standing RA, but only 12% of 33 patients with PsA, 6% of 34 patients with OA and 3% of 93 control sera. Lower frequencies for these diseases were obtained on testing for antibodies against CB11: 50%, 6%, 21% and 2%, respectively. The sensitivity of detection in RA of antibodies against CB10 compared with antibodies against intact CII (88% versus 24%) was not at the expense of specificity, which remained high at 94%. The much higher frequency of antibodies against CB10 in RA than in other rheumatic diseases or control sera indicates that CB10 is clearly a more sensitive substrate than the intact collagen molecule and, combined with other assays (rheumatoid factor, anti-cyclic citrullinated peptide [anti-CCP]), might comprise a panel with a highly reliable predictive value. Moreover, our findings should encourage renewed interest in the role of collagen autoimmunity in the pathogenesis of RA.
Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic articular inflammation and progressive joint destruction. Autoimmunity to type II collagen (CII), an abundant molecule in articular cartilage, is implicated in pathogenesis because the immunization of susceptible strains of rats, mice and nonhuman primates using native CII in adjuvant results in collagen-induced arthritis (CIA), which has close immunologic and pathologic similarities to RA. CIA is dependent on immune responses to CII by both T and B lymphocytes, with arthritis being initiated by complement-fixing autoantibodies that bind to CII in the cartilage matrix. In humans, IgG-producing B cells specific for CII are present in rheumatoid synovium and synovial fluid, suggesting an intra-articular antigen-driven immune process. Serum autoantibodies against native and denatured type II collagen (anti-NCII and DCII) are detected in 24–30% of patients with RA, as shown by cross-sectional studies on patients with well-established disease. However, this relatively low frequency in RA of anti-CII, together with seropositivity (albeit at even lower frequency) in other rheumatological and inflammatory diseases including psoriatic arthritis (PsA), osteoarthritis (OA), juvenile arthritis, Paget's disease, and systemic lupus erythematosus, has negated the diagnostic utility and pathogenetic significance of anti-CII in RA. However, several studies have reported that the frequency of anti-NCII might be as high as 60–75% in patients with RA when tested very early in the disease, and thereafter frequencies tend to fall to those ascertained in the earlier cross-sectional studies, suggesting that their presence might provide a sensitive predictive marker for cases of early RA.
Our interest in the reactivity of RA sera with various cleavage products of CII led to the present study, in which we assess whether purified preparations of the two major cyanogen bromide (CNBr) fragments of CII, namely CB10 and CB11, would serve as superior substrates for the detection of antibodies in RA. It was found that the frequency of antibodies against CB10 in cases of well-established RA was markedly increased, from 24% to 88%, comparing the frequency using the intact CII molecule; this was not at the expense of the specificity, which remained at the high level of 94%.
Antibodies against intact type II collagen (CII) are a feature of rheumatoid arthritis (RA) but have limited diagnostic value. Here we assess whether either of the two major cyanogen bromide fragments of CII, namely CB10 or CB11, are more sensitive substrates for the detection of antibodies in RA. Cleavage of bovine CII with cyanogen bromide yielded CB10 and CB11; these were purified by column chromatography for use in an enzyme-linked immunosorbent assay. Serum antibodies were measured in patients with RA, psoriatic arthritis (PsA), osteoarthritis (OA) and blood donors. Results were compared with those using intact CII. Antibodies against CB10 were found in as many as 88% of 96 patients with long-standing RA, but only 12% of 33 patients with PsA, 6% of 34 patients with OA and 3% of 93 control sera. Lower frequencies for these diseases were obtained on testing for antibodies against CB11: 50%, 6%, 21% and 2%, respectively. The sensitivity of detection in RA of antibodies against CB10 compared with antibodies against intact CII (88% versus 24%) was not at the expense of specificity, which remained high at 94%. The much higher frequency of antibodies against CB10 in RA than in other rheumatic diseases or control sera indicates that CB10 is clearly a more sensitive substrate than the intact collagen molecule and, combined with other assays (rheumatoid factor, anti-cyclic citrullinated peptide [anti-CCP]), might comprise a panel with a highly reliable predictive value. Moreover, our findings should encourage renewed interest in the role of collagen autoimmunity in the pathogenesis of RA.
Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic articular inflammation and progressive joint destruction. Autoimmunity to type II collagen (CII), an abundant molecule in articular cartilage, is implicated in pathogenesis because the immunization of susceptible strains of rats, mice and nonhuman primates using native CII in adjuvant results in collagen-induced arthritis (CIA), which has close immunologic and pathologic similarities to RA. CIA is dependent on immune responses to CII by both T and B lymphocytes, with arthritis being initiated by complement-fixing autoantibodies that bind to CII in the cartilage matrix. In humans, IgG-producing B cells specific for CII are present in rheumatoid synovium and synovial fluid, suggesting an intra-articular antigen-driven immune process. Serum autoantibodies against native and denatured type II collagen (anti-NCII and DCII) are detected in 24–30% of patients with RA, as shown by cross-sectional studies on patients with well-established disease. However, this relatively low frequency in RA of anti-CII, together with seropositivity (albeit at even lower frequency) in other rheumatological and inflammatory diseases including psoriatic arthritis (PsA), osteoarthritis (OA), juvenile arthritis, Paget's disease, and systemic lupus erythematosus, has negated the diagnostic utility and pathogenetic significance of anti-CII in RA. However, several studies have reported that the frequency of anti-NCII might be as high as 60–75% in patients with RA when tested very early in the disease, and thereafter frequencies tend to fall to those ascertained in the earlier cross-sectional studies, suggesting that their presence might provide a sensitive predictive marker for cases of early RA.
Our interest in the reactivity of RA sera with various cleavage products of CII led to the present study, in which we assess whether purified preparations of the two major cyanogen bromide (CNBr) fragments of CII, namely CB10 and CB11, would serve as superior substrates for the detection of antibodies in RA. It was found that the frequency of antibodies against CB10 in cases of well-established RA was markedly increased, from 24% to 88%, comparing the frequency using the intact CII molecule; this was not at the expense of the specificity, which remained at the high level of 94%.