Granzyme B and perforin: constitutive expression in human polymorphonuclear neutrophils

Genetic variants of human granzyme B predict transplant outcomes after HLA matched unrelated bone marrow transplantation for myeloid malignancies

Serine protease granzyme B plays important roles in infections, autoimmunity, transplant rejection, and antitumor immunity. A triple-mutated granzyme B variant that encodes three amino substitutions (Q48R, P88A, and Y245H) has been reported to have altered biological functions. In the polymorphism rs8192917 (2364A>G), the A and G alleles represent wild type QPY and RAH mutant variants, respectively. In this study, we analyzed the impact of granzyme B polymorphisms on transplant outcomes in recipients undergoing unrelated HLA-fully matched T-cell-replete bone marrow transplantation (BMT) through the Japan Donor Marrow Program. The granzyme B genotypes were retrospectively analyzed in a cohort of 613 pairs of recipients with hematological malignancies and their unrelated donors. In patients with myeloid malignancies consisting of acute myeloid leukemia and myelodysplastic syndrome, the donor G/G or A/G genotype was associated with improved overall survival (OS; adjusted hazard ratio [HR], 0.60; 95% confidence interval [CI], 0.41–0.89; P = 0.01) as well as transplant related mortality (TRM; adjusted HR, 0.48; 95% CI, 0.27–0.86, P = 0.01). The recipient G/G or A/G genotype was associated with a better OS (adjusted HR, 0.68; 95% CI, 0.47–0.99; P = 0.05) and a trend toward a reduced TRM (adjusted HR, 0.61; 95% CI, 0.35–1.06; P = 0.08). Granzyme B polymorphism did not have any effect on the transplant outcomes in patients with lymphoid malignancies consisting of acute lymphoid leukemia and malignant lymphoma. These data suggest that there is an association between the granzyme B genotype and better clinical outcomes in patients with myeloid malignancies after unrelated BMT.

Malignant catarrhal fever induced by Alcelaphine herpesvirus 1 is characterized by an expansion of activated CD3+CD8+CD4- T cells expressing a cytotoxic phenotype in both lymphoid and non-lymphoid tissues

Alcelaphine herpesvirus 1 (AlHV-1) is carried by wildebeest asymptomatically. It causes a fatal lymphoproliferative disease named wildebeest-derived malignant catarrhal fever (WD-MCF) when cross-species transmitted to a variety of susceptible species of the Artiodactyla order. WD-MCF can be reproduced experimentally in rabbits. In a previous report, we demonstrated that WD-MCF induced by AlHV-1 is associated with a severe proliferation of CD8(+) T cells in the lymphoid tissues. Here, we further studied the mononuclear leukocytic populations in both the lymphoid (throughout the infection and at time of euthanasia) and non-lymphoid (at time of euthanasia) organs during WD-MCF induced experimentally in rabbits. To reach that goal, we performed multi-colour flow cytometry stainings. The results obtained demonstrate that the development of WD-MCF correlates in peripheral blood with a severe increase of CD8(+) cell percentages; and that CD3(+)CD8(+)CD4(-) T cells were the predominant cell type in both lymphoid and non-lymphoid organs at time of euthanasia. Further characterization of the mononuclear leukocytes isolated from both lymphoid and non-lymphoid tissues revealed that the CD8(+) T cells express high levels of the activation markers CD25 and CD44, produce high amount of gamma-interferon (IFN-γ) and perforin, and showed a reduction of interleukin-2 (IL-2) gene expression. These data demonstrate that the development of WD-MCF is associated with the expansion and infiltration of activated and cytotoxic CD3(+)CD8(+)CD4(-) T cells secreting high amount of IFN-γ but low IL-2.

Control of granzymes by serpins

Although proteolysis mediated by granzymes has an important role in the immune response to infection or tumours, unrestrained granzyme activity may damage normal cells. In this review, we discuss the role of serpins within the immune system, as specific regulators of granzymes. The well-characterised human granzyme B-SERPINB9 interaction highlights the cytoprotective function that serpins have in safeguarding lymphocytes from granzymes that may leak from granules. We also discuss some of the pitfalls inherent in using rodent models of granzyme-serpin interactions and the ways in which our understanding of serpins can help resolve some of the current, contentious issues in granzyme biology.

Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma

The cytotoxic granzyme B (GrB)/perforin pathway has been traditionally viewed as a primary mechanism that is used by cytotoxic lymphocytes to eliminate allogeneic, virally infected and/or transformed cells. Although originally proposed to have intracellular and extracellular functions, upon the discovery that perforin, in combination with GrB, could induce apoptosis, other potential functions for this protease were, for the most part, disregarded. As there are 5 granzymes in humans and 11 granzymes in mice, many studies used perforin knockout mice as an initial screen to evaluate the role of granzymes in disease. However, in recent years, emerging clinical and biochemical evidence has shown that the latter approach may have overlooked a critical perforin-independent, pathogenic role for these proteases in disease. This review focuses on GrB, the most characterized of the granzyme family, in disease. Long known to be a pro-apoptotic protease expressed by cytotoxic lymphocytes and natural killer cells, it is now accepted that GrB can be expressed in other cell types of immune and nonimmune origin. To the latter, an emerging immune-independent role for GrB has been forwarded due to recent discoveries that GrB may be expressed in nonimmune cells such as smooth muscle cells, keratinocytes, and chondrocytes in certain disease states. Given that GrB retains its activity in the blood, can cleave extracellular matrix, and its levels are often elevated in chronic inflammatory diseases, this protease may be an important contributor to certain pathologies. The implications of sustained elevations of intracellular and extracellular GrB in chronic vascular, dermatological, and neurological diseases, among others, are developing. This review examines, for the first time, the multiple roles of GrB in disease pathogenesis.

Live Candida albicans suppresses production of reactive oxygen species in phagocytes

Production of reactive oxygen species (ROS) is an important aspect of phagocyte-mediated host responses. Since phagocytes play a crucial role in the host response to Candida albicans, we examined the ability of Candida to modulate phagocyte ROS production. ROS production was measured in the murine macrophage cell line J774 and in primary phagocytes using luminol-enhanced chemiluminescence. J774 cells, murine polymorphonuclear leukocytes (PMN), human monocytes, and human PMN treated with live C. albicans produced significantly less ROS than phagocytes treated with heat-killed C. albicans. Live C. albicans also suppressed ROS production in murine bone marrow-derived macrophages from C57BL/6 mice, but not from BALB/c mice. Live C. albicans also suppressed ROS in response to external stimuli. C. albicans and Candida glabrata suppressed ROS production by phagocytes, whereas Saccharomyces cerevisiae stimulated ROS production. The cell wall is the initial point of contact between Candida and phagocytes, but isolated cell walls from both heat-killed and live C. albicans stimulated ROS production. Heat-killed C. albicans has increased surface exposure of 1,3-beta-glucan, a cell wall component that can stimulate phagocytes. To determine whether surface 1,3-beta-glucan exposure accounted for the difference in ROS production, live C. albicans cells were treated with a sublethal dose of caspofungin to increase surface 1,3-beta-glucan exposure. Caspofungin-treated C. albicans was fully able to suppress ROS production, indicating that suppression of ROS overrides stimulatory signals from 1,3-beta-glucan. These studies indicate that live C. albicans actively suppresses ROS production in phagocytes in vitro, which may represent an important immune evasion mechanism.

Death by a thousand cuts: granzyme pathways of programmed cell death

The granzymes are cell death-inducing enzymes, stored in the cytotoxic granules of cytotoxic T lymphocytes and natural killer cells, that are released during granule exocytosis when a specific virus-infected or transformed target cell is marked for elimination. Recent work suggests that this homologous family of serine esterases can activate at least three distinct pathways of cell death. This redundancy likely evolved to provide protection against pathogens and tumors with diverse strategies for evading cell death. This review discusses what is known about granzyme-mediated pathways of cell death as well as recent studies that implicate granzymes in immune regulation and extracellular proteolytic functions in inflammation.

Neutrophils in antibody-based immunotherapy of cancer

Monoclonal antibodies (mAb) are presently considered key therapeutic drugs for the treatment of malignancies. They can be designed to specifically target tumour-associated antigens and initiate several effector mechanisms, which potentially leads to elimination of the tumour. Through their Fc tail mAbs interact with Fc receptors (FcR) that are expressed on immune cells. Neutrophils are the most abundant circulating FcR-expressing white blood cells with potent cytotoxic ability that is enhanced in the presence of antitumour mAbs. They furthermore play a role in regulating adaptive immunity, which may lead to the initiation of antitumour immune responses. Yet, neutrophils receive surprisingly little attention as potential effector cell population. This article reviews the scientific data that supports the possibility of exploiting neutrophils for mAb-based immunotherapy of cancer. An increasing awareness and understanding of this topic may allow for future development of new anticancer therapies.

Activation of the granzyme pathway in children with severe respiratory syncytial virus infection

Granzymes (Grs), serine proteases present in granules of effector lymphocytes, are involved in several host immune responses, including the activation of cell death and inflammatory pathways. The main goal of this study was to determine whether the local cell-mediated Gr pathway is activated during severe respiratory syncytial virus (RSV) lower respiratory tract illness (LRTI) in children. Tracheal aspirates (TA) from 23 children with RSV-LRTI and 12 controls without pulmonary disease were analyzed for Gr A and B. Bronchoalveolar lavage fluid samples from seven children with RSV-LRTI were analyzed for cellular expression of GrB. Levels of GrA and GrB in TA were significantly increased in RSV patients compared with controls and both Grs showed preserved activity. Gr levels correlated with the total leukocyte counts and IL-8 levels in the airways at several time points. However, no correlation between Gr levels and release of caspase-cleaved cytokeratin-18 was found. There was evidence for marked expression of GrB by both CD8(+) and CD4(+) T cells and natural killer cells in the respiratory tract. These findings suggest activation of the cell-mediated Gr pathway during severe RSV-LRTI in children.

Expression of granzyme B in peripheral blood polymorphonuclear neutrophils (PMN), myeloid cell lines and in PMN derived from haemotopoietic stem cells in vitro

Granzyme B and perforin are the major protagonists of cytotoxicity mediated by natural killer (NK) cells or cytotoxic T cells. More recent we described the presence of granzyme B and perforin in polymorphonuclear neutrophils (PMN), a finding in discrepancy with the credo that granzyme B and perforin expression is restricted to cytotoxic T cells and NK cells. In extension of our previous study, we now provide evidence that granzyme B is not only present in mature PMN, but also in the myeloid cell lines HL-60 and U937, in CD34+ stem cells, and in PMN derived from CD34+ cells in vitro. In agreement with the "targeting by time" hypothesis we found the bulk of granzyme B in association with primary granules, in addition to a minor membrane expression. Granzyme B, on one hand might, enhance the cytotoxic potential of PMN, on the other, it may provide PMN with additional means to degrade extracellular matrices.

Granzyme B and natural killer (NK) cell death

Granzyme B is a unique serine protease, which plays a crucial role for target cell death. Several mechanisms of delivery of granzyme B to target cells have been recently identified. Granzyme B directly activates Bid, a specific substrate for granzyme B, resulting in caspase activation. Granzyme B efficiently cleaves many prominent autoantigens, and the hypothesis that autoantibodies arise when cryptic determinants are revealed to the immune system has been proposed. Some autoantibodies directed against granzyme B-specific neoepitopes are present in serum from patients with autoimmune diseases. In the tissues from autoimmune diseases, granzyme B might play an important role for disease progression (i.e., rheumatoid arthritis synovium) or inhibition (i.e., regulatory T cells). We have identified a novel type of activation-induced cell death (granzyme B leakage-induced cell death). Activation-induced natural killer (NK) cell death is accompanied by the leakage of granzyme B from intracellular granules into the cytoplasm, and it triggers apoptosis by directing Bid to mitochondrial membranes. An excess of "leaked" granzyme B over its inhibitor, serpin proteinase inhibitor 9, is a major determinant of cell death. The role of granzyme B in autoimmunity and its influence on NK cell death are discussed.

Intimate Cell Conjugate Formation and Exchange of Membrane Lipids Precede Apoptosis Induction in Target Cells during Antibody-Dependent, Granulocyte-Mediated Cytotoxicity

Ab-dependent polymorphonuclear granulocyte (PMN)-mediated cytotoxicity may play an important role in the control of malignant diseases. However, little is known as to which particular pathways are used for the killing of malignant cells by PMN. The production of reactive oxygen intermediates (ROI) has been observed to occur during Ab-dependent, cell-mediated cytotoxicity (ADCC). However, PMN from a patient with chronic granulomatous disease demonstrated strong ADCC against malignant lymphoma cells. Furthermore, the inhibition of ROI production in PMN from healthy donors had no significant effect on ADCC. Therefore, ROI production by the NADPH oxidase of PMN does not appear to be mandatory for PMN-mediated ADCC. Recent data suggest a role for perforins in PMN-mediated cytotoxicity. However, in our assays concanamycin A, an inhibitor of perforin-mediated ADCC by mononuclear cells, had no inhibitory effect on PMN-mediated ADCC. Using electron microscopy we observed that PMN and their target cells intimately interact with the formation of interdigitating membrane protrusions. During PMN and target cell contact there was a mutual exchange of fluorescent membrane lipid dyes that was strongly increased in the presence of tumor-targeting Abs. This observation may be closely related to the recently described process of trogocytosis by lymphocytes. The presence of transient PMN-tumor cell aggregates and the accumulation of PMN with tumor cell-derived membrane lipids and vice versa were associated with effective ADCC as measured by chromium-release or apoptosis induction.

Human mast cells produce and release the cytotoxic lymphocyte associated protease granzyme B upon activation

Mast cells are widely distributed throughout the body and express effector functions in allergic reactions, inflammatory diseases, and host defense. Activation of mast cells results in exocytosis of preformed chemical mediators and leads to novel synthesis and secretion of lipid mediators and cytokines. Here, we show that human mast cells also express and release the cytotoxic lymphocyte-associated protease, granzyme B. Granzyme B was active and localized in cytoplasmic granules, morphologically resembling those present in cytotoxic lymphocytes. Expression and release of granzyme B by mast cell-lines HMC-1 and LAD 2 and by cord blood- and mature skin-derived human mast cells depended on the mode of activation of these cells. In mast cell lines and cord blood-derived mast cells, granzyme B expression was mainly induced by non-physiological stimuli (A23187/PMA, Compound 48/80) and substance P. In contrast, mature skin-derived mast cells only produced granzyme B upon IgE-dependent stimulation. We conclude that granzyme B is expressed and released by human mast cells upon physiologic stimulation. This suggests a role for granzyme B as a novel mediator in mast cell biology.

The humoral pattern recognition receptor PTX3 is stored in neutrophil granules and localizes in extracellular traps

The long pentraxin (PTX) 3 is produced by macrophages and myeloid dendritic cells in response to Toll-like receptor agonists and represents a nonredundant component of humoral innate immunity against selected pathogens. We report that, unexpectedly, PTX3 is stored in specific granules and undergoes release in response to microbial recognition and inflammatory signals. Released PTX3 can partially localize in neutrophil extracellular traps formed by extruded DNA. Eosinophils and basophils do not contain preformed PTX3. PTX3-deficient neutrophils have defective microbial recognition and phagocytosis, and PTX3 is nonredundant for neutrophil-mediated resistance against Aspergillus fumigatus. Thus, neutrophils serve as a reservoir, ready for rapid release, of the long PTX3, a key component of humoral innate immunity with opsonic activity.

Expression of granzyme A in human polymorphonuclear neutrophils

Polymorphonuclear neutrophils (PMNs) are the first line of defence against invading pathogens. They contain a multitude of antimicrobial and potentially cytotoxic substances packed in granules and secretory vesicles. Here, we show that granzyme A (GzmA) is constitutively expressed in human PMNs, but not in the promyelocytic cell line HL-60, by performing flow cytometry, western blot, enzyme-linked immunosorbent assay and quantitative polymerase chain reaction. To further track the intracellular localization of GzmA, we performed subcellular fractionation and found GzmA to be present in peroxidase-negative granules. Finally, stimulation with opsonized Escherichia coli or the bioincompatible haemodialysis membrane cuprophane led to up-regulation of GzmA expression at the transcriptional level as well as at the translational level. In conclusion, we provide clear evidence that GzmA is constitutively expressed in human PMNs and can be up-regulated upon stimulation. These findings may also indicate a role for GzmA in PMNs in defence against invading pathogens.

Granzyme B induction signalling pathway in acute myeloid leukemia cell lines stimulated by tumor necrosis factor alpha and Fas ligand

Acute myeloid leukemia (AML) cell lines treated by genotoxic agents or by Tumor Necrosis Factor alpha (TNFalpha) acquire potent cytotoxicity towards myeloid cells through activation of granzyme B (GrB)/perforin (PFN) system. Here we first extend this observation to another death receptor activator, Fas Ligand (FasL). Moreover, we analyzed GrB induction signalling pathway in TNFalpha- and FasL-stimulated AML cells. The effects of TNFalpha and FasL on GrB expression were specifically mediated by p38MAPK (Mitogen-activated-protein-kinase) activation. Otherwise, TNFalpha and FasL stimulation led to radical oxygen species (ROS) generation and ASK1 (Apoptosis-signal-regulating-kinase-1) activation. Endogenous activation of ASK1 by either H2O2 or thioredoxin (Trx) reductase inhibition had the same effects as TNFalpha and FasL on GrB up regulation. Altogether, our results suggest that TNFalpha- and FasL-stimulated AML cell lytic induction is regulated by a signalling pathway involving sequentially, ROS generation, Trx oxidation, ASK1 activation, p38MAPK stimulation and GrB induction at mRNA and protein levels.

Granzyme B, a novel mediator of allergic inflammation: its induction and release in blood basophils and human asthma

Histamine, leukotriene C4, IL-4, and IL-13 are major mediators of allergy and asthma. They are all formed by basophils and are released in particularly large quantities after stimulation with IL-3. Here we show that supernatants of activated mast cells or IL-3 qualitatively change the makeup of granules of human basophils by inducing de novo synthesis of granzyme B (GzmB), without induction of other granule proteins expressed by cytotoxic lymphocytes (granzyme A, perforin). This bioactivity of IL-3 is not shared by other cytokines known to regulate the function of basophils or lymphocytes. The IL-3 effect is restricted to basophil granulocytes as no constitutive or inducible expression of GzmB is detected in eosinophils or neutrophils. GzmB is induced within 6 to 24 hours, sorted into the granule compartment, and released by exocytosis upon IgE-dependent and -independent activation. In vitro, there is a close parallelism between GzmB, IL-13, and leukotriene C4 production. In vivo, granzyme B, but not the lymphoid granule marker granzyme A, is released 18 hours after allergen challenge of asthmatic patients in strong correlation with interleukin-13. Our study demonstrates an unexpected plasticity of the granule composition of mature basophils and suggests a role of granzyme B as a novel mediator of allergic diseases.

[Granzymes A and B in pulmonary sarcoidosis (experimental study)]

Sarcoidosis is a systemic disease of unknown aetiology, morphologically characterized by well-formed epithelioid granulomas, which show little or no central necrosis. These may be present in any organ or tissue. The lung is the most frequently and prominently involved target. The granuloma is often very sharply demarcated from the adjacent tissue and is surrounded by a mantle of lymphocytes, which mediate lysis of target cells by various mechanisms, including exocytosis of lytic proteins, perforins and granzymes. Sarcoidosis laboratorial diagnosis is usually made by SACE and Lisozyme dosages. The granzymes A and B could be two other markers of the disease, since the sarcoidosis granuloma is rich in cytotoxic and NK cells. An ELISA Kit was used to measure Granzyme A and B in serum of a normal control group (NC) (n=30), and in two groups with lung pathology: one without sarcoidosis, disease control (DC) (n=21) and other with sarcoidosis (S) (n=11). Our results showed that SACE activity is significantly augmented in S group comparing with NC and DC, respectively: 82,6+/-32,7/31,9+/-17,8 - p=0,00017 and 82,6+/-32,7/31,9+/-17,8 - p=0,00024. Lisozyme activity is significantly augmented in S and DC groups comparing with NC. Granzyme B showed a significant decrease in DC and S groups comparing with NC. Granzyme A showed a significant decrease between S/NC groups. Our results suggest that the decrease of Granzyme A and B in sarcoidotic patients could be related to an ineffective inflammatory local response related to the formation of sarcoidosis granulomas. More studies are needed, particularly in BAL.

TNFα stimulates NKG2D-mediated lytic activity of acute myeloid leukemic cells

The mechanism by which leukemic cells interfere with normal hematopoiesis remains unclear. We show here that, whereas the leukemic KG1a cells are naturally devoid from cellular cytotoxicity, once activated by TNFalpha, they display cytolytic activity toward various cellular targets including CFU-GM. This mechanism is dependent on stimulation of the granzyme B/perforin system. In addition, KG1a cells expressed the NKG2D receptor and its signal-transducing adaptator DAP 10, which were functional as confirmed by redirected lysis experiments. Interestingly, flow cytometry analysis of 20 samples of patients with acute myeloid leukemia (AML) (FAB M0-M5) revealed the expression of NKG2D (40%) and other natural cytotoxicity receptors (40% for NKp30, 74% for NKp44, 39% for NKp46) by a pool >15% of leukemic cells. Furthermore, CD34+ hematopoietic progenitors undergoing granulomonocytic differentiation expressed NKG2D ligands. Altogether, we propose a model in which, upon stimulation by TNFalpha, leukemic cells may exert cytotoxicity against myeloid progenitors. This finding may have important clinical implications in the context of diseases characterized by TNFalpha accumulation, such as AML or myelodisplasic syndromes.

Quiescent and activated mouse granulocytes do not express granzyme A and B or perforin: similarities or differences with human polymorphonuclear leukocytes?

Polymorphonuclear leukocytes have been shown to use a multitude of effector functions to combat pathogens and tumors, including enzymes, defensins, and toxic products such as oxygen radicals and nitrogen oxides. Recent studies provided evidence for the expression of granzymes (gzms) and perforin (perf) within the cytotoxic arsenal of human neutrophils, the validity of which was questioned by 2 subsequent studies. We have now used cytology, intracellular flow cytometry, enzymatic assays, immunoelectron microscopy, and quantitative reverse transcriptase-polymerase chain reaction to obtain evidence of the presence of gzms and/or perf in mouse Gr-1+ granulocyte populations. The data obtained clearly demonstrate that neither in vitro- nor in vivo-derived mouse granulocytes synthesize gzmA and gzmB or perf, even following infection/immunization with pathogens or pathogen-derived material. A parallel comparable analysis on the expression of gzmB in human neutrophils from 3 healthy control subjects and 4 patients with diverse diseases failed to detect gzmB expression. The data indicate that polymorphonuclear leukocytes from mice and humans lack the 3 cytotoxic effector molecules, gzmA, gzmB, and perf, generally associated with natural killer and cytotoxic T lymphocytes. (Blood. 2005;106:2871-2878)

Differential expression of the granzymes A, K and M and perforin in human peripheral blood lymphocytes

Granzymes (Gzm) are a group of serine proteases which are stored in the granules of cytotoxic lymphocytes. In humans, five granzymes have been characterized to date at the molecular level. While GzmA and GzmB have been extensively studied, little is known about GzmH, GzmK and GzmM. In this study, we describe the generation of mAbs against human GzmK and GzmM by genetic immunization. The obtained anti-GzmK and anti-GzmM mAbs are not cross-reactive with GzmA, GzmB, GzmM and GzmA, GzmB, GzmK, respectively, and show a granular staining pattern in human lymphocytes. Flow cytometric analysis of peripheral blood lymphocytes revealed that GzmA, GzmM and perforin show a similar distribution. They are expressed in almost all CD16+CD56+ NK cells, CD3+CD56+ NKT cells and gammadelta T cells as well as in 20-30% of all CD3+CD8+ TC cells. Surprisingly, GzmK was not detected in the highly cytotoxic CD16+CD56+ NK cells but was preferentially expressed in lymphocytes of the T cell lineage, staining 20% of CD3+CD8+ TC cells, 50% of CD3+CD56+ NKT cells and 40% of gammadelta T cells, as well as 60% of the small sub-population of CD56bright+ NK cells. Our data suggest that human granzymes are differentially expressed in distinct sub-populations of peripheral blood lymphocytes.

[The role of neutrophils during allograft rejection]

Because rejection of allografts is primarily caused by T and B lymphocyte responses to allogeneic histocompatibility molecules, the role of innate immunity in organ transplant rejection is often overlooked. However, the very first damages to vascularized organ allografts are caused by ischemia-reperfusion, an inflammatory reaction involving activation of vascular endothelial cells and release of neutrophil chemoattractants. Herein, we review experimental observations suggesting that the early neutrophil influx in organ transplants favors T cell-mediated rejection.

Elastase and granzymes during meningococcal disease in children: correlation to disease severity

OBJECTIVE

To investigate the levels of human neutrophil elastase and lymphocyte-derived granzymes A and B in relation to disease severity in children with meningococcal disease.

DESIGN

Clinical observational cohort study.

SETTING

Paediatric intensive care unit.

PATIENTS

All patients with meningococcal disease during the study period were included.

MEASUREMENTS AND RESULTS

Blood sampling was done on the day of admission and on days 3 and 7. Assays for elastase and granzymes were done with ELISA. Sixty-one patients were included: 19 having distinct meningitis; 17 meningitis and shock; and 25 fulminant septicaemia. On admission levels of elastase were increased in all patients, being highest in those with fulminant septicaemia and lowest in those with distinct meningitis. Granzyme A (although marginally) and granzyme B levels were only increased in patients with shock. In 20 of the 28 patients admitted for > or = 3 days elastase decreased from admission ("rapid-decrease" group). In the remaining 8 patients, elastase started to decrease after 2 days ("slow-decrease" group). Patients of the "slow-decrease" group had a higher temperature up to day 4, needed more respiratory support (mean airway pressure in cm H2O on days 3 and 4: p=0.02 and p<0.01, respectively), and more circulatory support (>2 inotropic agents on day 3; p=0.04) compared with the "rapid-decrease" group.

CONCLUSIONS

Human neutrophil elastase and granzyme B are related with disease severity during the initial phase of meningococcal disease and prolonged neutrophil activation is associated with the extent of organ dysfunction during the period thereafter.

Gene expression signatures in neutrophils exposed to glucocorticoids: A new paradigm to help explain “neutrophil dysfunction” in parturient dairy cows

Neutrophils are the first line of immunity against most pathogens that infect cattle. These normally short-lived white blood cells develop from myeloid-lineage cells in bone marrow. Upon maturation, bone marrow neutrophils are released into the circulation where they marginate on inflamed blood vessel endothelial cells and migrate through them into the area of infection. Once migrated, neutrophils do not reenter the circulation, but rather, perform their bactericidal functions and die by apoptosis in the tissue. The cytokine and hormonal milieu of the blood and extracellular tissue fluid can influence neutrophil development and immunity-related activities, but the molecular basis of these phenotypic changes and physiological benefits or drawbacks of them are poorly understood. In the current paper, we review new gene expression information that resulted from two of our functional genomics studies designed to evaluate effects of glucocorticoid hormones on bovine neutrophils. This work provides one model to describe complex changes that occur in neutrophils as the cells respond to glucocorticoids, which might act to alter the cells' functional priorities and tip the delicate balance between health and disease during stress, including at parturition. A bovine immunobiology microarray and real time RT-PCR were used to study blood neutrophils collected during the natural surge of endogenous glucocorticoid (cortisol) in parturient dairy cows and bone marrow neutrophils collected from glucocorticoid (dexamethasone)-treated dairy steers. The gene expression signatures we observed led us to perform additional phenotyping of the neutrophils and correlation analyses, which together painted a picture suggesting that glucocorticoids have key roles in modulating neutrophil development, life span, and tissue defense functions during parturition and hormone therapy. Based on these observations, we postulate that glucocorticoids orchestrate adaptive changes in the entire neutrophil system that support increased cell numbers and longevity in blood and heightened remodeling activity in tissues, while at the same time decreasing some important antimicrobial defense activities of the cells. Thus, our functional genomics studies have enabled us to elucidate multiple consequences of neutrophil exposure to glucocorticoids, highlighting a probable role for this interaction in the induction of parturition and partly explaining why some parturient dairy cows may experience heightened incidence and severity of inflammatory diseases like mastitis.

Granzyme B Induces Smooth Muscle Cell Apoptosis in the Absence of Perforin

OBJECTIVE

T cell-induced cytotoxicity, of which granzyme B is a key mediator, is believed to contribute to the pathogenesis of inflammatory vascular diseases. In this report, we investigate the mechanism of granzyme B-induced smooth muscle cell (SMC) death.

METHODS AND RESULTS

The addition of purified granzyme B alone to cultured SMCs caused a significant reduction in cell viability. Chromatin condensation, phosphatidylserine externalization, and membrane blebbing were observed, indicating that the mechanism of granzyme B-induced SMC death was through apoptosis. Activated splenocytes from perforin-knockout mice induced SMC death through a granzyme B-mediated pathway. Inhibition of the proteolytic activities of caspases and granzyme B prevented granzyme B-induced SMC death, whereas attenuation of granzyme B internalization with mannose-6-phosphate (M6P) did not. Further, granzyme B induced the cleavage of several SMC extracellular proteins, including fibronectin, and reduced focal adhesion kinase phosphorylation.

CONCLUSIONS

These results indicate that granzyme B can induce apoptosis of SMCs in the absence of perforin by cleaving extracellular proteins, such as fibronectin.

Prevalence and clinical significance of resistance to perforin- and FAS-mediated cell death in leukemia

Killer lymphocytes play a central therapeutic role in graft-versus-leukemia following allogeneic hematopoietic stem cell transplantation (HSCT). The Perforin/Granzyme and FAS/CD95 pathways are of crucial importance in tumor cell elimination by killer cells. In this study, we have examined whether hematological malignancies are resistant to perforin and anti-FAS antibodies. Leukemic cells were studied from 29 patients suffering either from acute or chronic myeloid leukemia (AML or CML), acute or chronic lymphoid leukemia, or non-Hodgkin's lymphoma. An average of 49 vs 5% of specific cell killing was found when using perforin vs anti-FAS antibodies, respectively. Interestingly, resistance towards both perforin and anti-FAS antibodies was found exclusively in leukemic cells from patients with myeloid leukemia. Analysis of leukemic cells from patients with CML, suffering from leukemia relapse after HSCT and given donor lymphocyte infusion (DLI) to induce remission, indicated that the effectiveness of treatment with DLI was not associated with sensitivity of leukemic cells to perforin. In conclusion, resistance towards anti-FAS antibodies is a common phenomenon in leukemia/lymphoma, whereas perforin resistance occurs only in myeloid leukemia. However, as a single parameter, perforin resistance does not appear to be suitable to predict the outcome of DLI.

Proteolysis of the Pericellular Matrix

The 2 major general concepts about the cell biology of atherogenesis, growth of smooth muscle cells, and lipid accumulation in macrophages, ie, foam cell formation, have not been able to satisfactorily explain the genesis of acute coronary syndromes. Rather, the basic pathology behind the acute atherothrombotic events relates to erosion and rupture of unstable coronary plaques. At the cellular level, we now understand that a switch from cellular growth to cellular death, notably apoptosis, could be involved in turning at least some types of atherosclerotic plaques unstable. Because intimal cells require a proper matrix environment for normal function and survival, the vulnerability of an atherosclerotic plaque may critically depend on the integrity of the pericellular matrix of the plaque cells. In vitro studies have revealed that plaque-infiltrating inflammatory cells, such as macrophages, T-lymphocytes, and mast cells, by secreting a variety of proteases capable of degrading pericellular matrix components, induce death of endothelial cells and smooth muscle cells, and so provide a mechanistic explanation for inflammation-dependent plaque erosion and rupture. Thus, a novel link between inflammation and acute coronary syndromes is emerging. For a more explicit understanding of the role of proteases released by inflammatory cells in the conversion of a clinically silent plaque into a dangerous and potentially killing plaque, animal models of plaque erosion and rupture need to be established.

Amplification of T-cell responses by neutrophils: relevance to allograft immunity

Because rejection of allografts is primarily caused by T and B lymphocyte responses to allogenic histocompatibility molecules, the role of innate immunity in organ transplant rejection is often overlooked. However, the very first damages to vascularized organ allografts are caused by ischemia-reperfusion, an inflammatory reaction involving activation of vascular endothelial cells and release of neutrophil chemoattractants. Herein, we review experimental observations suggesting that the early neutrophil influx in organ transplants favors T cell-mediated rejection.