Figure 1.

Recognition of citrulline-containing peptide (CCP) epitopes by Anti-citrullinated peptide/protein antibodies (ACPA) as detected by multipin and conventional ELISA. (a), (b) Multipin ELISA. (a) Reactivity of 53 sera from rheumatoid arthritis (RA) patients (black triangle), 46 sera from CCP-negative non-RA patients patients (white triangle) and 45 sera from healthy volunteers (circle) with the fil306–326 (upper panel) and the fil ³¹¹TXGRS³¹⁵ (lower panel) epitopes synthethized on the pin. The calculated area under the curve of ROC (AUC) was 0·7748 for the fil306–326, and 0·8034 for the 5-mer peptide, respectively. (b) Comparison of RA (n = 33) and healthy (n = 16) sera’s reactivity against the fil306–326 epitope (upper left), the double citrulline-containing fil311–315 (upper right), vim65–77 (lower left) and coll359–369 (lower right). Differences between RA and healthy groups were significant, P < 0·0002, P < 0·0001, P < 0·0258, and P < 0·001, respectively. (c–f) Conventional ELISA. Reactivities of RA (n = 198), CCP-negative systemic lupus erythematosus patients (n = 18) or healthy (n = 138) sera samples with: (c) C-terminally biotinylated fil306–326, (d) fil ³¹¹TXGRS³¹⁵ with Ttds linker, (e) vim65–77, and (f) coll359–369 peptides bound to neutravidin pre-coated plates. The sensitivity values were 62%, 60%, 44% and 41%, respectively. ROC curve analysis has shown AUC values 0·7991 for fil306–326, 0·7593 for fil311–315-Ttds-biotin, 0·787 for vim65–77, and 0·6258 for coll359–369.