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  • Title: Expression and function of the co-stimulator H4/ICOS on activated T cells of patients with rheumatoid arthritis.
    Author: Okamoto T, Saito S, Yamanaka H, Tomatsu T, Kamatani N, Ogiuchi H, Uchiyama T, Yagi J.
    Journal: J Rheumatol; 2003 Jun; 30(6):1157-63. PubMed ID: 12784384.
    Abstract:
    OBJECTIVE: To investigate the expression and function of the inducible co-stimulator H4/ICOS in rheumatoid arthritis (RA) patients. H4/ICOS is the newest member of the CD28/CTLA-4 family to have been found to be expressed on activated T cells, and it participates in a variety of important immunoregulatory functions. METHODS: The levels of H4/ICOS expression on T cells among peripheral blood mononuclear cells (PBMC) and synovial fluid mononuclear cells (SFMC) from 28 patients with RA were analyzed by flow cytometry. To explore the role of H4/ICOS function in the inflammation of rheumatoid joints, lymphokine production by SF CD4+ T cells co-stimulated by H4/ICOS was assayed. Expression of H4/ICOS ligand (B7RP-1) mRNA in synovial tissues from patients with RA was examined by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: H4/ICOS-positive cells were increased significantly in whole, CD4+, and CD8+ T-cell fractions of SFMC compared with control PBMC. Comparison between control PB and PB from patients with active RA showed that H4/ICOS-positive whole and CD8+ T-cell fractions were increased significantly in the PB of RA patients. H4/ICOS costimulation clearly increased interferon-g, interleukin 4 (IL-4), and IL-10 production by SF CD4+ T cells. By RT-PCR, RA synovial tissue was shown to express mRNA of B7RP-1. CONCLUSION: Our results suggest that local immune responses may be modulated by H4/ICOS expressed on T cells in the joints of patients with RA, and thus H4/ICOS may be involved in the pathogenetic mechanism of RA.
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