| 1. |
- Aybay, Erdem, et al.
(author)
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Extended cleavage specificities of human granzymes A and K, two closely related enzymes with conserved but still poorly defined functions in T and NK cell-mediated immunity
- 2023
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In: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 14
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Journal article (peer-reviewed)abstract
- Granzymes A and K are two highly homologous serine proteases expressed by mammalian cytotoxic T cells (CTL) and natural killer cells (NK). Granzyme A is the most abundant of the different granzymes (gzms) expressed by these two cell types. Gzms A and K are found in all jawed vertebrates and are the most well conserved of all hematopoietic serine proteases. Their potential functions have been studied extensively for many years, however, without clear conclusions. Gzm A was for many years thought to serve as a key component in the defense against viral infection by the induction of apoptosis in virus-infected cells, similar to gzm B. However, later studies have questioned this role and instead indicated that gzm A may act as a potent inducer of inflammatory cytokines and chemokines. Gzms A and K form clearly separate branches in a phylogenetic tree indicating separate functions. Transcriptional analyses presented here demonstrate the presence of gzm A and K transcripts in both CD4+ and CD8+ T cells. To enable screening for their primary biological targets we have made a detailed analysis of their extended cleavage specificities. Phage display analysis of the cleavage specificity of the recombinant enzymes showed that both gzms A and K are strict tryptases with high selectivity for Arg over Lys in the P1 position. The major differences in the specificities of these two enzymes are located N-terminally of the cleavage site, where gzm A prefers small amino acids such as Gly in the P3 position and shows a relatively relaxed selectivity in the P2 position. In contrast, gzm K prefers large amino acids such as Phe, Tyr, and Trp in both the P2 and P3 positions and does not tolerate negatively charged residues in the P2 position. This major distinction in extended specificities is likely reflected also in preferred in vivo targets of these two enzymes. This information can now be utilized for high-precision screening of primary targets for gzms A and K in search of their highly conserved but still poorly defined functions in vertebrate immunity.
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| 2. |
- Cardenas, Eduardo, I, et al.
(author)
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Elastase- and LPS-Exposed Cpa3(Cre/+) and ST2(-/-) Mice Develop Unimpaired Obstructive Pulmonary Disease
- 2022
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In: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 13
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Journal article (peer-reviewed)abstract
- IL-33 and its receptor ST2, as well as mast cells and their mediators, have been implicated in the development of chronic obstructive pulmonary disease (COPD). However, whether mast cells and the ST2 receptor play a critical role in COPD pathophysiology remains unclear. Here, we performed repeated intranasal administrations of porcine pancreatic elastase and LPS for four weeks to study COPD-like disease in wildtype, ST2-deficient, and Cpa3(Cre/+) mice, which lack mast cells and have a partial reduction in basophils. Alveolar enlargement and changes in spirometry-like parameters, e.g. increased dynamic compliance and decreased expiratory capacity, were evident one day after the final LPS challenge and worsened over time. The elastase/LPS model also induced mild COPD-like airway inflammation, which encompassed a transient increase in lung mast cell progenitors, but not in mature mast cells. While ST2-deficient and Cpa3(Cre/+) mice developed reduced pulmonary function uninterruptedly, they had a defective inflammatory response. Importantly, both ST2-deficient and Cpa3(Cre/+) mice had fewer alveolar macrophages, known effector cells in COPD. Elastase/LPS instillation in vivo also caused increased bronchiole contraction in precision cut lung slices challenged with methacholine ex vivo, which occurred in a mast cell-independent fashion. Taken together, our data suggest that the ST2 receptor and mast cells play a minor role in COPD pathophysiology by sustaining alveolar macrophages.
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| 3. |
- Mendez-Enriquez, Erika, et al.
(author)
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Mast Cells and Their Progenitors in Allergic Asthma
- 2019
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In: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 10
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Research review (peer-reviewed)abstract
- Mast cells and their mediators have been implicated in the pathogenesis of asthma and allergy for decades. Allergic asthma is a complex chronic lung disease in which several different immune cells, genetic factors and environmental exposures influence the pathology. Mast cells are key players in the asthmatic response through secretion of a multitude of mediators with pro-inflammatory and airway-constrictive effects. Well-known mast cell mediators, such as histamine and bioactive lipids are responsible for many of the physiological effects observed in the acute phase of allergic reactions. The accumulation of mast cells at particular sites of the allergic lung is likely relevant to the asthma phenotype, severity and progression. Mast cells located in different compartments in the lung and airways have different characteristics and express different mediators. According to in vivo experiments in mice, lung mast cells develop from mast cell progenitors induced by inflammatory stimuli to migrate to the airways. Human mast cell progenitors have been identified in the blood circulation. A high frequency of circulating human mast cell progenitors may reflect ongoing pathological changes in the allergic lung. In allergic asthma, mast cells become activated mainly via IgE-mediated crosslinking of the high affinity receptor for IgE (Fc epsilon RI) with allergens. However, mast cells can also be activated by numerous other stimuli e.g. toll-like receptors and MAS-related G protein-coupled receptor X2. In this review, we summarize research with implications on the role and development of mast cells and their progenitors in allergic asthma and cover selected activation pathways and mast cell mediators that have been implicated in the pathogenesis. The review places an emphasis on describing mechanisms identified using in vivo mouse models and data obtained by analysis of clinical samples.
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| 4. |
- Salomonsson, Maya, et al.
(author)
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Localization-Specific Expression of CCR1 and CCR5 by Mast Cell Progenitors
- 2020
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In: Frontiers in Immunology. - : FRONTIERS MEDIA SA. - 1664-3224. ; 11
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Journal article (peer-reviewed)abstract
- Mast cells are powerful immune cells found predominately in barrier tissues. They play an important role in immune surveillance and act as effector cells in allergic reactions. Mast cells develop from mast cell progenitors (MCp), which migrate to the peripheral tissues via the blood circulation. Presumably, the homing of MCp to the peripheral sites and localization is regulated by chemotactic signals. Due to the scarce abundance of these cells, chemotactic receptors have not been previously characterized on primary MCp. Here, mRNA transcripts for CCR1 and CX(3)CR1 were identified in mouse bone marrow and lung MCp in a gene expression screen of chemotactic receptors. However, surface expression of CCR1 was only found in the bone marrow MCp. Flow cytometry-based screening identified distinct surface expression of CCR5 by mouse peritoneal mast cells and MCp, while surface expression of CXCR2-5, CX(3)CR1, CCR1-3, CCR6-7, and CCR9 was not detected. Low surface expression of CCR5 was detected in mouse MCp in the bone marrow, spleen, and lung. To translate the findings to human, blood and bone marrow MCp from healthy donors were analyzed for possible CCR1 and CCR5 expression. Human MCp showed distinct surface expression of both CCR1 and CCR5. The expression levels of these chemokine receptors were higher in human bone marrow MCp than in the peripheral blood, suggesting that CCR1 and CCR5 may mediate retention in the bone marrow. In conclusion, mouse and human MCp show differential expression of CCR1 and CCR5 depending on their localization.
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| 5. |
- Zarnegar, Behdad, et al.
(author)
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Influenza Infection in Mice Induces Accumulation of Lung Mast Cells through the Recruitment and Maturation of Mast Cell Progenitors
- 2017
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In: Frontiers in Immunology. - : FRONTIERS MEDIA SA. - 1664-3224. ; 8
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Journal article (peer-reviewed)abstract
- Mast cells (MCs) are powerful immune cells that mature in the peripheral tissues from bone marrow (BM)-derived mast cell progenitors (MCp). Accumulation of MCs in lung compartments where they are normally absent is thought to enhance symptoms in asthma. The enrichment of lung MCs is also observed in mice subjected to models of allergic airway inflammation. However, whether other types of lung inflammation trigger increased number of MCp, which give rise to MCs, is unknown. Here, mouse-adapted H1N1 influenza A was used as a model of respiratory virus infection. Intranasal administration of the virus induced expression of VCAM-1 on the lung vascular endothelium and an extensive increase in integrin beta 7(hi) lung MCp. Experiments were performed to distinguish whether the influenza-induced increase in the number of lung MCp was triggered mainly by recruitment or in situ cell proliferation. A similar proportion of lung MCp from influenza-infected and PBS control mice were found to be in a proliferative state. Furthermore, BM chimeric mice were used in which the possibility of influenza-induced in situ cell proliferation of host MCp was prevented. Influenza infection in the chimeric mice induced a similar number of lung MCp as in normal mice. These experiments demonstrated that recruitment of MCp to the lung is the major mechanism behind the influenza-induced increase in lung MCp. Fifteen days post-infection, the influenza infection had elicited an immature MC population expressing intermediate levels of integrin beta 7, which was absent in controls. At the same time point, an increased number of toluidine blue(+) MCs was detected in the upper central airways. When the inflammation was resolved, the MCs that accumulated in the lung upon influenza infection were gradually lost. In summary, our study reveals that influenza infection induces a transient accumulation of lung MCs through the recruitment and maturation of MCp. We speculate that temporary augmented numbers of lung MCs are a cause behind virus-induced exacerbations of MC-related lung diseases such as asthma.
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| 6. |
- Zarnegar, Behdad, et al.
(author)
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Innate Immunity Induces the Accumulation of Lung Mast Cells During Influenza Infection
- 2018
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In: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 9
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Journal article (peer-reviewed)abstract
- Mast cells release disease-causing mediators and accumulate in the lung of asthmatics. The most common cause of exacerbations of asthma is respiratory virus infections such as influenza. Recently, we demonstrated that influenza infection in mice triggers the recruitment of mast cell progenitors to the lung. This process starts early after infection and leads to the accumulation of mast cells. Previous studies showed that an adaptive immune response was required to trigger the recruitment of mast cell progenitors to the lung in a mouse model of allergic lung inflammation. Therefore, we set out to determine whether an adaptive immune response against the virus is needed to cause the influenza-induced recruitment of mast cell progenitors to the lung. We found that influenza-induced recruitment of mast cell progenitors to the lung was intact in Rag2(-/-) mice and mice depleted of CD4(+) cells, implicating the involvement of innate immune signals in this process. Seven weeks after the primary infection, the influenza-exposed mice harbored more lung mast cells than unexposed mice. As innate immunity was implicated in stimulating the recruitment process, several compounds known to trigger innate immune responses were administrated intranasally to test their ability to cause an increase in lung mast cell progenitors. Poly I:C, a synthetic analog of viral dsRNA, induced a TLR3-dependent increase in lung mast cell progenitors. In addition, IL-33 induced an ST2-dependent increase in lung mast cell progenitors. In contrast, the influenza-induced recruitment of mast cell progenitors to the lung occurred independently of either TLR3 or ST2, as demonstrated using Tlr3(-/-) or Il1rl1(-/-) mice. Furthermore, neutralization of IL-33 in Tlr3(-/-) mice could not abrogate the influenza-induced influx of mast cell progenitors to the lung. These results suggest that other innate receptor(s) contribute to mount the influx of mast cell progenitors to the lung upon influenza infection. Our study establishes that mast cell progenitors can be rapidly recruited to the lung by innate immune signals. This indicates that during life various innate stimuli of the respiratory tract trigger increases in the mast cell population within the lung. The expanded mast cell population may contribute to the exacerbations of symptoms which occurs when asthmatics are exposed to respiratory infections.
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