They could additionally damage myocardial tissue, because MHC class I proteins

disappeared in the central infarction sites, whereas their expression was conserved, but weaker in the surrounding peri-necrotic zones of the MI 1 week after an acute coronary event when compared to myocardial tissue sections of persons who died 5 weeks after an acute coronary event. It find more suggests susceptibility of peri-infarction zones for NK cell killing mediated by cytotoxic mediators. GNLY+ CD3+ cells and rarely GNLY+ CD56+ cells reach the apoptotic APAF-1+ cardiomyocytes in the border infiltration zone of persons who died 1 week after the acute coronary event and could participate in the apoptosis of these cells. Accordingly, apoptotic single-stranded DNA–positive cells were found in the border zones and granulation tissue cells in the infarct region by Akasaka et al. [7]. But, it is unlikely that GNLY+ cells cause significant cardiomyocytes apoptosis because of their small

numbers. In addition, later after the MI, the APAF-1+ apoptotic myocardial cells are found without close contact with GNLY+ cells, suggesting implementation of GNLY-independent mechanism of cellular loss. A formation of apoptosome after the binding of APAF-1 protein with cytochrome C could induce caspase 9 dimerization and autocatalysis [32]. Indeed, apoptotic markers (caspase 3 and apoptotic bodies) are present in the surviving zone of the heart, remote from the infarct region, as early as day 1 after MI and persist for up to 1 month

[3, 33]. Additionally, NADPH-cytochrome-c2 reductase www.selleckchem.com/products/BIBW2992.html on day 7 after an acute coronary event, the significant increase in the percentage of peripheral blood GNLY+ NK cells enables GNLY-mediated K-562 apoptosis, as the mechanism attributed to perforin-mediated cytotoxicity [31]. GNLY probably accesses the K562 target cell cytoplasm through perforin pores or by other mechanisms that involve sublytic perforin concentrations in agreement with Lettau et al. [18], because an additive effect between GNLY- and perforin-mediated cytotoxicity has not been found. This suggests that they probably use the same mechanism for entering cells. On day 14, in patients with NSTEMI, GNLY expression, as well as perforin expression [31], in all peripheral blood lymphocyte subpopulations was the lowest and it was reflected in negligible NK cell apoptotic activity against K-562 cells. The lower percentage of GNLY-positive NK cells in patients with NSTEMI on day 21 as compared to day 7, correlated well with mostly perforin-mediated NK cell killing as a redundant apoptotic mechanism [27]. At the end of a 1-month rehabilitation period in patients with NSTEMI, we again found significant participation of GNLY in K562 apoptosis as a result of restored GNLY expression in peripheral blood NK cells.