Apoptosis in idiopathic inflammatory myopathies with partial invasion; a role for CD8+ cytotoxic T cells?

Polymyositis and inclusion body myositis are idiopathic inflammatory myopathies, with a pathology characterized by partial invasion of non-necrotic muscle fibres by CD8+ cytotoxic T-cells, leading to fibre degeneration. Although the main effector pathway of CD8+ T-cells is to induce apoptosis of target cells, it has remained unclear if apoptosis occurs in these diseases, and if so, if it is mediated by CD8+ T-cells. In consecutive biopsy sections from 10 patients with partial invasion, muscle fibres and inflammatory cells were assessed by immunohistochemistry and apoptotic nuclei by the TUNEL assay. Analysis of muscle fibre morphology, staining pattern and quantification were performed on digital images, and they were compared with biopsies from 10 dermatomyositis patients and 10 controls without muscle disease. Apoptotic myonuclei were found in muscle with partial invasion, but not in the invaded fibres. Fibres with TUNEL positive nuclei were surrounded by CD8+ T-cells, granzyme B+ cells and macrophages, but lacked FAS receptor expression. In contrast, apoptotic myonuclei were rare in dermatomyositis and absent in controls. The findings confirm that apoptosis occurs in idiopathic inflammatory myopathies and support that it is mediated by CD8+ cytotoxic T- cells, acting in parallel to the process of partial invasion.

TUNEL: a useful screening method in sudden cardiac death.

The primary objective of this study was to investigate if detection of apoptosis in the heart can be used to diagnose early myocardial ischaemia. The material consisted of myocardial tissue from autopsy cases: 10 cases with occlusive, thrombotic coronary artery disease and acute myocardial infarction, 10 cases of sudden cardiac death without coronary artery disease (CAD) and 8 controls without cardiovascular disease and with known causes of death. Necrotic changes in the myocardium were detected with hematoxylin-erythrosin-saffron, Mallory's PTAH stain and with antibodies against complement 9. Apoptotic nuclei were visualised with two different kits using the terminal deoxynucleotidyl transferase-mediated desoxyuridinetriphosphate nick end-labeling (TUNEL) method on histological sections. In the patients with CAD, early myocardial infarction was found in one defined area of the ventricular wall; apoptotic myocyte nuclei were observed not in the necrotic lesions, but evenly spread usually without a gradient, all over the myocardium with a mean number per high power field of 29% (range 3-56%) of the total number of myocyte nuclei. In the sudden cardiac deaths without CAD, necrosis was scarce and distributed both focally and irregularly in both the left and right ventricular walls. With few exceptions, the percentage of apoptotic myocyte nuclei exceeded 20% in all sections (mean 24%, range 0-68%). No difference was seen between patients with CAD and those without CAD (p > 0.05). With the TUNEL method, positively stained nuclei were seen very early and extensively all over the myocardium. It is not certain that they represent true apoptosis induced by ischemia, but TUNEL appears to be a useful screening method in cases where sudden cardiac death is suspected.