The primary protein in cartilage, Type II Collagen (CII) is crucial to joint health and function. Yet, the involvement of CII in the process of joint inflammation has proven difficult to substantiate. To gain a clearer understanding of CII's role in the pathogenesis of RA, researchers at Queen Mary, University of London and others studied its behaviour within an inflamed joint, when modified by oxidants linked to inflammation or by ribose, a five-carbon sugar common to all living cells.
For their investigation, the researchers collected blood serum samples from 31 RA patients. For control purposes, serum samples were also collected from 41 patients with other inflammatory joint diseases. Both RA and non-RA samples were analyzed for their ability to bind to pure and natural CII and to CII that had been chemically modified. The modified CII included three oxidants present in the rheumatic joint – hydroxyl radical, hypochlorous acid, and peroxynitrite – and ribose.
Of the 31 RA serum samples analyzed, only 3 showed antibody binding to natural CII – affirming this protein as an innocent bystander in autoimmunity and its inflammatory toll on the joints. However, the percentage of samples that exhibited antibody binding increased 4-fold when tested with modified CII. In fact, 45 percent of all RA samples were assessed with moderate to strong antibody binding reactions. CII treated with hypochlorous acid was the most reactive, followed by CII treated with peroxynitrite, glycation, and hydroxyl radical, respectively.
"The present findings support the possibility that chemical modification of self antigens, in RA in particular and in inflammation in general, is the cause of formation of neoepitopes," reflects the study's leading author, Ahuva Nissim, Ph.D. "We propose that the oxidative modification of CII creates a CII autoantigen."
MEDICA.de; Source: John Wiley & Sons, Inc.