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Fig. 1 | Arthritis Research & Therapy

Fig. 1

From: Anti-carbamylated protein antibodies precede disease onset in monkeys with collagen-induced arthritis

Fig. 1

Anti-carbamylated protein (anti-CarP) antibodies can be detected in rhesus monkeys, while anti-citrullinated protein antibodies (ACPA) and rheumatoid factor (RF) cannot. a Anti-CarP IgG antibodies were measured by ELISA. Carbamylated fetal calf serum (Ca-FCS) and the non-modified fetal calf serum (FCS) served as the (control) antigen. The open square indicates a human positive control and the last two available primate samples for each monkey are indicated in closed circles. b RF-IgM antibodies were measured by ELISA, using rabbit IgG as binding antigen. The open square indicates a human positive control and the last two available primate samples for each monkey are indicated in closed circles. c ACPA IgG antibodies were measured by ELISA, using several citrullinated and control peptides or proteins as antigens. The open square indicates a human positive control and the last two available primate samples for each monkey are indicated in closed circles. d Anti-CarP IgG antibodies are shown for both the first available sample, taken at the time point of immunization and the last available sample in comparison to each other. Antibodies were measured as in a. The absorbance values for the FCS were subtracted from the Ca-FCS absorbance values. All samples were measured on one plate. ELISAs were carried out using the 10 control monkeys that did not receive any (preventive) treatment (e). Anti-CarP IgG antibodies and clinical score are compared over time. The point of disease onset was set at 0. Disease onset was defined as the point at which the clinical score was higher than 0.5 and increased at the next time point. Also, a persistent clinical score >3 had to be present as well. Therefore, three monkeys had to be excluded from this analysis. The grey area indicates the average clinical score, while the black circles show the average levels of anti-CarP antibodies at that particular time point. f Correlation between anti-CarP antibodies and clinical score or anti-Collagen IgG antibodies was investigated. All time points in all 10 monkeys were included for this analysis. The presence of possible associations was tested by spearman correlation. CCP2, cyclic citrullinated peptide 2; cit, citrullinated; arg, arginine control; Fib, fibrinogen; MBP, myelin basic protein; AU/ml, arbitrary units per millilitre; ELISA, enzyme-linked immunosorbent assay

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