ACPA induce pathogenic cytokines expression in PBMC of ACPA+-RA patients and inhibition of its effect by Cit-ME a synthetic citrullinated peptide.

Smadar Gertel¹, Gidi Karmon¹, Eszter Szarka², Esther Houri-Levi³, Edna mozes⁴, Yehuda Shoenfeld¹ and Howard Amital^1,3.

¹ Zabludowicz Center For Autoimmune Diseases, Sheba Medical Center, Tel-Hashomer, Israel. ² Department of Immunology, Eötvös Loránd University, Budapest, Hungary. ³ Department of Medicine ‘B’, Sheba Medical Center, Tel-Hashomer, Israel. ⁴ Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel.  

Background/Purpose : Anti citrullinated protein autoantibodies (ACPA) are the major autoantibodies in rheumatoid arthritis (RA). ACPAs are directed against different citrullinated antigens, including filaggrin, fibrinogen, vimentin and collagen. Presence of ACPA is associated with joint damage and extra-articular manifestations, suggesting that ACPA are most likely arthritogenic autoantibodies in RA.

Methods: To verify the effect of ACPA on RA immune cells, PBMCs from ACPA⁺-RA patients and healthy controls were co-cultured in vitro with ACPA. Binding of the latter to the cells were analyzed by flow cytometry and effect on cytokines mRNA expression by real-time PCR. The stimulating effects induced by ACPA were manipulated by addition of Cit-ME a novel multi-epitope citrullinated peptide.

Results: ACPA bound specifically to PBMCs from ACPA⁺-RA patients via the Fab portion. ACPA induced an obvious pathogenic cytokine expression (4-13 fold increment) in immune cells derived from ACPA⁺-RA patients. Moreover, ACPA up-regulated the IL-1b and IL-6 mRNA expression levels by 10 and 6, folds, respectively compared to control IgG.

Cit-ME, a genuine ligand for ACPA, inhibited the ACPA-induced up-regulation of Il-1b and Il-6 by 50% [Fig.].  

Conclusion: ACPA binds to immune peripheral cells and enhances the synthesis of pathogenic cytokine expression. Together, these data suggests that ACPA is involved in the pathogenic effects in RA. Targeting ACPA in order to decrease its pathogenic capacity might provide a novel direction in the development of therapeutic strategies for RA.

Figure- ACPA induce IL-1b and IL-6 mRNA up-regulation. The Cit-ME, a multi-epitope citrullinated peptide, inhibited part of the ACPA cytokine up-regulation.