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Immunohistochemical analysis of perforin and granzyme A in inflammatory myopathies
1National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Tokyo, Japan.
Abstract:
Perforin (PF) and granzyme A (GA) are candidates suspected of being cytolytic proteins of the granules of cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. We analysed PF and GA in muscles from patients with inflammatory myopathies. Five cases of polymyositis (PM), two cases of inclusion body myositis (IBM), and five cases of dermatomyositis (DM) were studied immunohistochemically using anti-PF and GA antibodies raised against each synthetic peptide of human PF and mouse GA, together with a panel of monoclonal antibodies reactive for lymphocyte subsets. In PM and IBM, PF positive cells were colocalized with GA positive cells and occasionally invaded into the non-necrotic muscle fibres. The percentage of PF positive cells among the endomysial CD8 positive cell population was 9.9% (PM) and 12.5% (IBM), and the majority of the endomysial CD8 positive cells were alpha/beta T cells. In contrast, in DM, both PF and GA positive cells were very few in all cases. Only few inflammatory cells were CD16+ or CD57+ NK cells among these diseases. Our results suggest that PF and GA are secreted mainly from alpha/beta T cells, and may play a key role in muscle fibre damage in at least some PM and IBM, but not in DM.
Insights
Perforin and granzyme A are key proteins in cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. These proteins may cause muscle fiber damage in polymyositis and inclusion body myositis but not dermatomyositis.
Area of Science:
- Immunology
- Cell Biology
- Neurology
Background:
- Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells utilize cytotoxic proteins like perforin (PF) and granzyme A (GA) for cell lysis.
- Inflammatory myopathies, including polymyositis (PM), inclusion body myositis (IBM), and dermatomyositis (DM), involve muscle inflammation and damage.
- The specific roles of PF and GA in the pathogenesis of different inflammatory myopathies remain to be fully elucidated.
Purpose of the Study:
- To investigate the presence and localization of perforin (PF) and granzyme A (GA) in muscle biopsies from patients with inflammatory myopathies.
- To determine the cellular sources of PF and GA within the inflamed muscle tissue.
- To assess the potential contribution of PF and GA to muscle fiber damage in PM, IBM, and DM.
Main Methods:
- Immunohistochemical analysis of muscle biopsies using antibodies against PF and GA.
- Utilized monoclonal antibodies to identify lymphocyte subsets, including CD8+ T cells and NK cells.
- Quantified the percentage of PF-positive cells within the CD8+ T cell population in PM and IBM.
Main Results:
- Perforin (PF) and granzyme A (GA) positive cells were found in muscles of patients with polymyositis (PM) and inclusion body myositis (IBM), often co-localizing and invading non-necrotic muscle fibers.
- In PM and IBM, 9.9% and 12.5% of endomysial CD8+ T cells, predominantly alpha/beta T cells, were PF-positive, respectively.
- In contrast, dermatomyositis (DM) showed very few PF and GA positive cells, with minimal presence of CD16+ or CD57+ NK cells.
Conclusions:
- Perforin (PF) and granzyme A (GA) are primarily secreted by alpha/beta T cells in the context of inflammatory myopathies.
- These cytotoxic proteins likely play a significant role in muscle fiber damage in polymyositis (PM) and inclusion body myositis (IBM).
- The findings suggest that PF and GA are not major contributors to muscle damage in dermatomyositis (DM).