Immune Netw.  2013 Aug;13(4):116-122. 10.4110/in.2013.13.4.116.

Role of Citrullinated Fibrinogen Peptides in the Activation of CD4 T Cells from Patients with Rheumatoid Arthritis

• Shin K
• Hong S
• Choi EH
• Lim MK
• Shim SC
• Ju JH
• Lee SH

• KMID: 2150776
• DOI: http://doi.org/10.4110/in.2013.13.4.116

Abstract

This study was conducted to determine whether CD4 T cell responses to citrullinated fibrinogen occur in patients with rheumatoid arthritis (RA), especially in HLA-DR4-positive subjects. Whole peripheral blood mononuclear cells (PBMCs) of RA patients and control subjects were stimulated with citrullinated fibrinogen peptides, and T-cell production of proliferation and proinflammatory cytokines, such as interferon-gamma(IFN-gamma) and interleukin-17A (IL-17A), were measured. In addition, CD4 T cells from RA patients were stimulated with the citrullinated fibrinogen peptide, Fib-alpha R84Cit, identified as a DRB1*0401-restricted T cell epitope in HLA-DR4 transgenic mice, and the degree of T cell activation was examined similarly. No proliferative responses to the citrullinated fibrinogen peptides were observed in whole PBMCs or CD4 T cells from RA patients. Furthermore, no increased production of IFN-gamma or IL-17A was found in whole PBMCs or CD4 T cells stimulated with the citrullinated fibrinogen peptides, although these cells responded to recall antigen, a mixture of tetanus toxoid, purified protein derivative (PPD) from Mycobacterium tuberculosis, and Candida albicans. The results of this study indicate that anti-citrulline immunity in RA patients may be mediated by fibrinogen because there is no evidence of CD4 T cell-mediated immune responses to citrullinated fibrinogen peptides.

Keyword

Rheumatoid arthritis (RA); Citrullinated fibrinogen (cFBG); CD4 T cell; HLA-DR4; Interferon-gamma(IFN-gamma); Interleukin-17A (IL-17A)

MeSH Terms

Animals
Arthritis, Rheumatoid
Candida albicans
Cytokines
Epitopes, T-Lymphocyte
Fibrinogen
HLA-DR4 Antigen
Humans
Interleukin-17
Mice
Mice, Transgenic
Mycobacterium tuberculosis
Peptides
T-Lymphocytes
Tetanus Toxoid
Cytokines
Epitopes, T-Lymphocyte
Fibrinogen
HLA-DR4 Antigen
Interleukin-17
Peptides
Tetanus Toxoid

Figure

• 

  Figure 1 Immune responses of PBMCs from RA patients to cFBG peptides. PBMCs from RA patients (n=17) were stimulated with either non-citrullinated or citrullinated fibrinogen (cFBG) peptides at indicated concentrations (µg/ml). IFN-γ secretion was quantified from culture supernatant of peptide-stimulated PBMCs (A). Similarly, IL-17 secretion was quantified from the supernatant (B). Cell proliferation was evaluated with a dilution of CFSE (C). Representative FACS results are shown (D) (un-stimulation in black [% division: 0.31] and recall antigen stimulation in gray line [% division: 16.5]). #p<0.01 compared with non-stimulation (-). *p<0.05 compared with non-stimulation. (+) represents a mixture of recall antigens.

• 

  Figure 2 CD4 T-cell responses of PBMCs from RA patients and control subjects to Fib-α R84Cit peptide. CD4 T cells from RA patients (n=34) were stimulated with non-citrullinated (NP) and citrullinated (CP) fibrinogen peptides in the presence of APCs. Cell proliferation was quantified by the incorporation of BrdU. The degree of cell proliferation was compared between stimulation and non-stimulation, and values represent the degree of well proliferation in individual samples (A). IFN-γ (B) and IL-17A (C) secretion was quantified from each peptide-stimulated culture supernatant by ELISA. Similarly, T-cell proliferation (D), and IFN-γ (E) and IL-17A (F) production of CD4 T cells from control subjects (n=17) are shown. ns=not significant.

• 

  Figure 3 CD4 T-cell responses of PBMCs from anti-CCP Ab/HLA-DRB1*04-positive RA patients to Fib-α R84Cit peptide. CD4 T cells from anti-CCP Ab/HLA-DRB1*04-positive RA patients (n=13) were stimulated with non-citrullinated (NP) and citrullinated (CP) fibrinogen peptides in the presence of APCs. Cell proliferation was quantified by the incorporation of BrdU (A). IFN-γ (B) and IL-17A (C) secretion was quantified from each peptide-stimulated culture supernatant by ELISA. ns=not significant.

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