CD4+and CD8+CD28(null) T Cells Are Cytotoxic to Autologous Muscle Cells in Patients With Polymyositis

• Objective. Inflammatory T cell infiltrates in the skeletal muscle tissue of patients with polymyositis are dominated by CD28-negative effector (CD28(null)) T cells of both the CD4 and CD8 lineage. These cells are potentially cytotoxic, and the aim of the present study was to develop a fully autologous cell culture system in which to investigate the functional contribution of such CD28(null) T cells to myotoxicity. Methods. In vitro cocultures of autologous skeletal muscle cells and T cell subsets obtained from 5 polymyositis patients were performed. Myotoxicity of T cells was quantified by calcein release and flow cytometric analyses. T cell degranulation was blocked with concanamycin A. Specific blocking of perforin, cytokines, and HLA was performed using antibodies. Results. Both CD4+CD28(null) and CD8+CD28(null) T cells induced more muscle cell death than did their CD28+ counterparts. Differentiated muscle cells (myotubes) were more sensitive to T cell-mediated cell death than were their precursors (myoblasts). Both CD8+ and CD4+ CD28(null) T cells displayed perforin polarization toward muscle cells and secreted higher levels of granzyme B and interferon-gamma (IFN gamma) in coculture than did CD28+ T cells. The myotoxic effects of CD28(null) T cells were reduced upon the blocking of perforin, cytokines, and HLA. Addition of IFN gamma or tumor necrosis factor did not induce skeletal muscle cell death in the absence of T cells; however, it did up-regulate HLA expression on muscle cells. Conclusion. Myotoxicity of CD4+ and CD8+ CD28(null) T cells is mediated by directed perforin-dependent killing and can be further influenced by IFN gamma-induced HLA expression on muscle cells. The data suggest that CD28(null) T cells are key effector cells that contribute to the muscle cell damage in polymyositis.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Reumatologi och inflammation (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Rheumatology and Autoimmunity (hsv//eng)

Nyckelord

Experimental Autoimmune Myositis

Monoclonal-Antibody Analysis

Acute Coronary Syndromes

Inclusion-Body Myositis

Rheumatoid-Arthritis

Inflammatory Myopathies

Mononuclear-Cells

Immunosuppressive Treatment

Costimulatory Molecules

Pathogenic Features

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