Fig. 4.

Anti-CarP antibodies bind to Ca-Fib via variable domains. (A) IgG reactivity against Fib, Ci-Fib, and Ca-Fib of 54 healthy controls and 214 RA patients was analyzed by ELISA. (B) Specificity of anti–Ca-Fib reactivity was confirmed using inhibition studies. One sample is shown, where data are expressed relative to inhibition with PBS. (C) The molecular nature of purified IgG and F(ab′)2 was confimed by Coomassie-stained SDS-PAGE gel. (D) F(ab′)2 fragments were generated from purified IgG of 2 anti-CarP–positive patients and two negative controls. Only F(ab′)2 from patients reacted with Ci-Fib and Ca-Fib. (E) Inhibition experiments confirm that also F(ab′)2 are not necessarily cross-reactive between Ci-Fib and Ca-Fib.