Background Rheumatoid arthritis (RA) is characterized by inflammation and circulating autoantibodies. Inflammatory cytokines and autoantibodies had been described as important molecules in the immunopathogenesis of the disease. However, whether inflammatory cytokines and autoantibodies together can discriminate between early RA, chronic RA and preclinical stages is currently unknown.
Objectives To evaluate the levels of the cytokines IL-1, IL-6, TNF, IL-8, IL12p70 and IL-10 and the autoantibodies RF and antibodies to cyclic citrullinated peptides (ACCP) to determine the expression differences between humans with clinical and preclinical stages of RA.
Methods Serum from patients with less than 2 years of diagnosis, eRA (n=10) and patients with chronic RA with more than 2 years with the disease (cRA; n=10) were collected. All cRA patients had received treatment with DMARD's. Serum sample from eRA patients treated for 4 months were collected for comparison as well (n=6). First-degree relatives of patients with RA were stratified in positive (ACCP+; n=12) or negative (ACCP-; n=12) to ACCP. Subjects without family history of autoimmune diseases were included in a healthy control group (HC; n=10). Serum levels of ACCP were evaluated using ELISA and RF was measured by nephelometry. Cytokines levels for each group were quantified by BD™ cytometric bead array in a FACS CANTO II. Statistical analysis for group comparisons was done using the Kruskal-Wallis or wilcoxon test for non-parametric data. p<0.05 was considered significant. LDA analysis was performed to evaluate the capacity of the cytokines and autoantibodies to differentiate between groups.
Results Serum was available from 54 subjects (74% women). Differences between groups were evaluated. All the healthy subjects (HC, ACCP- and ACCP+) were negative to RF. There were significant differences between levels of ACCP between patients and healthy subjects. We found significant differences (p<0.01) in serum concentration of IL-6, TNF-α and IL-10 between patients with RA (eRA and cRA) and the groups HC, ACCP- and ACCP+. IL-1β. There were significant differences (p<0.01) only between cRA and HC in levels of IL-8. The levels of IL-12p70 present significant differences only between eRA and relatives positive and negative to ACCP. LDA analysis demonstrates that using the levels of IL-6, IL-10, ACCP and RF together, 60% can be discriminated among healthy groups with low risk (HC and ACCP-) subjects with high risk (ACCP+), patients with early RA and patients with chronic RA. A 90% of subjects with chronic and early RA can be discriminated as patients, using the expression values of these cytokines and autoantibodies (IL-6, IL-10, ACCP and RF).
Conclusions Together, levels of ACCP, RF, IL-6 and IL-10 can discriminate the patients with early or chronic onset of RA and preclinical stages including the high-risk subjects. This strategy would improve the diagnosis, treatment and classification for RA patients.
Disclosure of Interest None declared