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The serine protease granzyme B is an essential component of the granule exocytosis pathway, a major apoptotic mechanism used by cytotoxic T lymphocytes and natural killer cells to induce target cell apoptosis. Granzyme B gene transcription is induced in activated lymphocytes upon antigenic stimulation, and several regulatory regions including CBF, AP-1, and Ikaros binding sites have been shown to be essential in the control of granzyme B promoter activation. Dexamethasone, a glucocorticoid that is widely used as an immunomodulatory and anti-inflammatory agent, inhibits granzyme B mRNA transcript in phytohemagglutinin-activated peripheral blood mononuclear cells. Transfection of a reporter construct containing the -148 to +60 region of the human granzyme B promoter demonstrated that this region was the target for dexamethasone repression. Mutation of Ikaros or AP-1 binding sites in the context of the granzyme B promoter demonstrated that both sites participate in dexamethasone-mediated inhibition of the granzyme B promoter activity. Electromobility shift assay revealed that dexamethasone abolished the binding of nuclear transcription factors to the Ikaros binding site and reduced AP-1 binding activity. These results indicate that dexamethasone is able to abrogate the transcriptional activity of the human granzyme B gene promoter by inhibiting the binding of nuclear factors at the AP-1 and Ikaros sites.

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Granzyme B serine protease is found in the granules of activated cytotoxic T cells and in natural and lymphokine-activated killer cells. This protease plays a critical role in the rapid induction of target cell DNA fragmentation. The DNA regulatory elements that are responsible for the specificity of granzyme B gene transcription in activated T-cells reside between nt -148 and +60 (relative to the transcription start point at +1) of the human granzyme B gene promoter. This region contains binding sites for the transcription factors Ikaros, CBF, Ets, and AP-1. Mutational analysis of the human granzyme B promoter reveals that the Ikaros binding site (-143 to -114) and the AP-1/CBF binding site (-103 to -77) are essential for the activation of transcription in phytohemagglutinin-activated peripheral blood lymphocytes, whereas mutation of the Ets binding site does not affect promoter activity in these cells.

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Perforin is the cytolytic pore-forming protein, which alone can be responsible for the lethal hit in one of the killing mechanisms used by natural killer (NK) cells or cytotoxic T lymphocytes. In this study, perforin expression was investigated in cord blood (CB) lymphocytes to determine their killing potential in vivo. The majority of CB CD3- NK cells had the protein. Compared with adult perforin-positive NK cells, a significantly lower percentage of cells expressing CD56 and CD57, the related neural cell adhesion molecules, was found (P = .0001). Perforin was also present in a unique immature CB NK-cell subset, characterized by cytoplasmic CD3 antigen (Ag) expression. In CB, very few CD8 perforin-positive T lymphocytes could be detected, but they were in significant numbers in adult peripheral blood (P = .02). A substantial proportion of these cells (70% +/- 23%) lacked the CD28 T-cell coactivation Ag, and they were able to exert NK-like, major histocompatibility complex nonrestricted cytolytic activity. CD4+ and gamma delta-T cells expressing perforin were absent from CB, but low numbers of such cells were detected in adult peripheral blood (P = .0001). Therefore, the spontaneous cytolytic activity of CB lymphocytes appeared to be dependent on well-represented perforin-positive NK cells, which were shown to efficiently lyse NK-sensitive target cells.

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To evaluate rejection episodes in lung-transplanted patients, we analyzed 31 bronchoalveolar lavage specimens for lymphocyte levels and lymphocyte expression of two intracytoplasmic activation markers, perforin, the pore-forming lytic protein, and granzyme B, a member of the serine esterase family. Using anti-human granzyme B and perforin mAbs, we show that their expression in alveolar lymphocytes is correlated with the severity of rejection as assessed by histological parameters and the patients' clinical status. The presence of these molecules may provide a prognostic parameter that will facilitate the patients' monitoring, particularly in cases with minimal acute lung rejection susceptible to rapid progression to severe rejection.

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We have investigated perforin and granzyme B expression in graft-infiltrating lymphocytes of patients who underwent heart transplantation. Those proteins are commonly present in the cytoplasmic granules of cytotoxic T lymphocytes and are released upon effector-target cell interaction. From 28 patients 103 endomyocardial biopsies were obtained and examined by histology and immunocytochemical analysis using relevant monoclonal antibodies. We found that "high" biopsy histological grades were associated with perforin and granzyme B expression in graft-infiltrating lymphocytes of patients with acute severe rejection crisis. In contrast, these markers were not detected in patients without rejection or during graft stabilization. Interestingly, in patients with mild rejection and "low" histological grades, two groups could be distinguished with a differential expression of the two intracytoplasmic proteins. The presence of perforin and granzyme B-expressing cells was found to be predictive of rapid progression to severe rejection, so that this situation required additional treatment; in contrast, their absence seemed to correlate with a good graft outcome without additional treatment. Moreover, perforin and granzyme B expression seemed to be down-regulated by immunosuppressive drugs, which coincided with graft stabilization. In conclusion, our data suggest that detection of granzyme B and perforin in graft-infiltrating lymphocytes might be helpful for routinely monitoring heart transplant patients.

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CD3- large granular lymphocytes (LGL) are known to display natural killer cell (NK) activity without prior sensitization or restriction by major histocompatibility antigens. Upon short-term exposure to interleukin-2, NK cells were shown to acquire lymphocyte-activated killer cell (LAK) activity. The aim of this study was to analyze the characteristics of these lytic activities. Our data indicated that both NK and LAK activities were Ca2+ dependent; however, they could be dissociated by a Ca2+ channel blocker or a Ca2+ channel competitor agent. Moreover, NK activity was associated with granule exocytosis of lytic proteins spontaneously present in CD3- LGL, the most likely candidate being the pore-forming protein perforin. By contrast, LAK activity was found to be dependent on de novo protein synthesis and distinct from granule exocytosis. Our results strongly suggest that NK and LAK activities could be defined as two distinct pathways involving different lytic mediators.

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Monitoring of human allografts requires to use histological, immunohistochemical and functional techniques to characterize graft infiltrating cells. Granzyme B and perforin gene expression is of major importance in functional studies. Those proteins are present in the cytoplasmic granules of cytotoxic T lymphocytes and are secreted during granule exocytosis at the effector/target cell interface. Gene expression of both proteins has been studied by in situ hybridization using specific riboprobes on serial sections of biopsies in two pathological models. Our results show that cells infiltrating early skin lesions of patients with acute GVHD after bone marrow graft are exclusively composed of T cells, among which some of them express granzyme B and perforin genes. Similarly the presence of granzyme B and perforine-expressing cells in endomyocardial biopsies of heart transplanted patients has been associated to early and severe crisis of rejection. In contrast, the absence of functional markers in lymphoid infiltrates was coinciding with less aggressive and late episodes of rejection. Taken together, our data indicate that granzyme B and perforin gene expression in skin infiltrating lymphocytes during GVH or within heart infiltrating cells during crisis of rejection are in favor of severe processes. The study has allowed to predict during heart transplantation the apparition of a rejection crisis and to show the necessity for treating the patient with immunsuppresive drugs. This is also the case for patients with GVHD at the time of the first skin rash.

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Natural killer (NK) cells (CD3-) or large granular lymphocytes (LGL) spontaneously kill K562 targets but are unable to kill Daudi cells in the absence of IL-2 stimulation. IL-4 is reported to prevent or inhibit the IL-2-driven lymphokine-activated killer (LAK) generation in NK cells. Therefore, we wished to determine whether the antagonistic effect of IL-4 on IL-2-induced LAK activity might regulate the expression of genes encoding proteins involved in lysis, such as perforin, the pore-forming protein, or which are associated with lysis, such as granzymes A and B. By using in situ hybridization, we showed that, in addition to inducing LAK activity, IL-2 stimulation increased the amount of perforin and granzyme B mRNA at the single-cell level in 40 to 100% of the total CD3- LGL cell population. In addition, our results indicated that the stimulatory effect of IL-2 can be downregulated by IL-4 for both LAK activity and granzyme B and perforin gene expression. Here again, a decrease in the amount of specific mRNA per cell was noted. These findings suggest that modulation of the lytic machinery via lymphokines might be associated with regulation of the lytic potential of NK cells.

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