Citrullinated peptides are used for measuring anticitrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA). Accumulation of citrullinated proteins in the inflamed synovium suggests that they may be good targets for inducing peripheral tolerance. In view of the multiplicity of citrullinated autoantigens described as ACPA targets, we generated a multiepitope citrullinated peptide (Cit-ME) from the sequences of major citrullinated autoantigens: filaggrin, -fibrinogen, vimentin, and collagen type II. We assessed the ability of Cit-ME or the citrullinated 60-74 fibrinogen peptide (60-74-Fib-Cit) which bears immunodominant citrullinated epitopes (i) to modify cytokine gene expression and (ii) to modulate Treg and Th17 subsets in PBMC derived from newly diagnosed untreated RA patients. RA patient's PBMC incubated with Cit-ME or 60-74-Fib-Cit, showed upregulation of TGF- expression (16% and 8%, resp.), and increased CD4Foxp3 Treg (22% and 19%, resp.). Both peptides were shown to downregulate the TNF- and IL-1 expression; in addition, Cit-ME reduced CD3IL17 T cells. We showed that citrullinated peptides can modulate the expression of anti- and proinflammatory cytokines in PBMC from RA patients as well as the proportions of Treg and Th17 cells. These results indicate that citrullinated peptides could be active in vivo and therefore might be used as immunoregulatory agents in RA patients.