MHC class I-mediated cytotoxicity does not induce apoptosis in muscle fibers nor in inflammatory T cells: studies in patients with polymyositis, dermatomyositis, and inclusion body myositis
Abstract
Apoptosis plays a crucial role in natural recovery from T cell-mediated autoimmune disorders of the nervous system. Whether apoptosis also occurs in human inflammatory myopathies is unclear. In this study we examined muscle biopsy specimens from untreated patients with polymyositis (n = 12), dermatomyositis (n = 12), and inclusion body myositis (n = 12) for the presence of apoptosis using morphological criteria and DNA fragmentation by in situ tailing. In all these disorders, only rare T cells exhibited signs of apoptosis by nuclear morphology and in situ labeling techniques. Although Fas-expression was upregulated in a few inflammatory cells, increased apoptosis of the surrounding T cells was not observed. Further, nuclei of degenerating muscle fibers did not show morphological signs of apoptosis and were not labeled by the tailing reaction. We conclude that in the inflammatory myopathies, T cell inflammation is not cleared by apoptosis and affected muscle fibers do not die by apoptosis. The observations are consistent with the non-self-limited nature of these disorders and suggest that, in contrast to the nervous system, the local microenvironment in muscle does not deliver pro-apoptotic stimuli.
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Autoimmune Diseases
Autoimmune diseases occur as a result of an attack by the immune system on the body’s own tissues resulting in damage and dysfunction. There are different types of autoimmune diseases, in which there is a complex and unknown interaction between genetics and the environment. Discover the latest research on autoimmune diseases here.
Apoptosis
Apoptosis is a specific process that leads to programmed cell death through the activation of an evolutionary conserved intracellular pathway leading to pathognomic cellular changes distinct from cellular necrosis