IgG antibodies to type II collagen reflect inflammatory activity in patients with rheumatoid arthritis

Objective. To determine the clinical significance of IgG antibodies to type II collagen (CII) and to define any correlation of antibodies to CII with the inflammatory response in patients with rheumatoid arthritis (RA). Methods. IgG antibodies to native human type II collagen (IgG anti-CII) wer e measured in sera and synovial fluid (SF) from patients with RA, patients with osteoarthritis (OA), and healthy controls by an improved ELISA, Demogr aphic, clinical, and laboratory data including tumor necrosis factor-alpha (TNF-alpha) and interleukin 6 (IL-6) levels were also obtained at the time of sampling in patients with RA. Results. The median level and positivity for circulating IgG anti-CII were higher in patients with RA (n = 297) than patients with OA (n = 34) and hea lthy controls (n = 50) (p < 0.001). The titers of IgG anti-CII in SF were;a lso higher in RA (n = 45) than in OA (n = 16) (p < 0.001). In paired sample s, the levels of IgG anti-CII were significantly higher in SF compared to t he sera in patients with RA (n = 45) (p < 0.001), but levels were not diffe rent in patients with OA (n = 16). Circulating IgG anti-CII converted from positive to negative in 13 patients (10.7%) and from negative to positive i n 18 patients (14.8%) among 122 patients with RA in whom IgG anti-CII were monitored sequentially at a mean interval of 12.2 months. IgG anti-CII posi tive patients (n = 98) had shorter disease duration (p = 0.04) and less fre quent deformity (p = 0.013), and higher median erythrocyte sedimentation ra te (ESR) (p = 0.001) and C-reactive protein (CRP) (p < 0.001) than IgG anti -CII negative patients (n = 120). The levels of IgG anti-CII correlated wit h CRP (r = 0.270) and ESR (r = 0.253). CRP decreased significantly in patie nts (n = 13) who converted from IgG anti-CII positive to negative (p = 0.01 3). IgG anti-CII positive patients (n = 40) had higher levels of TNF-alpha and IL-6 than negative patients (n = 40) (p < 0.001). Levels of IgG anti-CI I correlated well with TNF-alpha (r = 0.617) and IL-6 (r = 0.347). Conclusion. Increased IgG anti-CII in sera and SF in RA correlated directly with acute phase reactants and the proinflammatory cytokines TNF-alpha and IL-6, Our data suggest that IgG anti-CII could reflect inflammatory activi ty with a potential to destroy cartilage in the early stages of RA.