Human neutrophils specifically interact with human monocyte-derived macrophage monolayers

Neutrophil elastase-dependent cleavage compromises the tumor suppressor role of EMILIN1

Proteolysis of the extracellular matrix (ECM) is a key event in tumor growth and progression. The breakdown of ECM can lead to the generation of bioactive fragments that promote cell growth and spread. EMILIN1, a multidomain glycoprotein expressed in several tissues, exerts a crucial regulatory function through the engagement of α4/α9 integrins. Unlike the majority of ECM molecules that elicit a proliferative program, the signals emitting from EMILIN1 engaged by α4/α9β1 integrins are antiproliferative. In this study, aimed to demonstrate if the suppressor role of EMILIN1 was related to its structural integrity, we tested the possibility that EMILIN1 could be specifically cleaved. Among the proteolytic enzymes released in the tumor microenvironment we showed that neutrophil elastase cleaved EMILIN1 in three/four major fragments. The consequence of this proteolytic process was the impairment of its anti-proliferative role. Accordingly, EMILIN1 was digested in sarcomas and ovarian cancers. Sarcoma specimens were infiltrated by neutrophils (PMNs) and stained positively for elastase. The present findings highlight the peculiar activity of PMN elastase in disabling EMILIN1 suppressor function.

Neutrophils activate alveolar macrophages by producing caspase-6-mediated cleavage of IL-1 receptor-associated kinase-M

Alveolar macrophages (AMs) are exposed to respirable microbial particles. Similar to phagocytes in the gastrointestinal tract, AMs can suppress inflammation after exposure to nonpathogenic organisms. IL-1R-associated kinase-M (IRAK-M) is one inhibitor of innate immunity, normally suppressing pulmonary inflammation. During pneumonia, polymorphonuclear neutrophils (PMNs) are recruited by chemotactic factors released by AMs to produce an intense inflammation. We report that intact IRAK-M is strongly expressed in resting human AMs but is cleaved in patients with pneumonia via PMN-mediated induction of caspase-6 (CASP-6) activity. PMN contact is necessary and PMN membranes are sufficient for CASP-6 induction in macrophages. PMNs fail to induce TNF-α fully in macrophages expressing CASP-6 cleavage-resistant IRAK-M. Without CASP-6 expression, PMN stimulation fails to cleave IRAK-M, degrade IκBα, or induce TNF-α. CASP-6(-/-) mice subjected to cecal ligation and puncture have impaired TNF-α production in the lung and decreased mortality. LPS did not induce or require CASP-6 activity demonstrating that TLR2/4 signaling is independent from the CASP-6 regulated pathway. These data define a central role for CASP-6 in PMN-driven macrophage activation and identify IRAK-M as an important target for CASP-6. PMNs de-repress AMs via CASP-6-mediated IRAK-M cleavage. This regulatory system will blunt lung inflammation unless PMNs infiltrate the alveolar spaces.

Ultrastructural evidence for human mast cell-eosinophil interactions in vitro

We have hypothesized that mast cells (MC) and eosinophils (Eos), the main effectors of allergy, can form an effector unit. These cells co-exist in the inflamed tissues during the late and chronic stages of allergy and have been shown to be capable of influencing each other's survival and activity via soluble mediators. We have recently described couples of receptor-ligands that are expressed on either/both of these cells and that imply a physical interaction. In this study, we have investigated the existence of short-term (60 min) in vitro interactions between human peripheral blood Eos and cord-blood-derived MC by transmission electron microscopy. We have found that MC and Eos adhere to each other; the lipid body content and the granule morphology of co-cultured MC and Eos, respectively, are altered, and the level of Eos peroxidase (EPO) released by co-cultured Eos is elevated. Moreover, the transfer of EPO from Eos to MC and tryptase from MC to Eos has been observed. Our results thus indicate that, when co-cultured, MC and Eos show signs of physical contact and of reciprocal activation. This is the first in vitro evidence of functional physical interactions between human MC and Eos, interactions that might also occur in vivo during allergic diseases.

Profiling CD antigens on leukaemias with an antibody microarray

Cluster of differentiation (CD) antigens are defined when a surface molecule found on some members of a standard panel of human cells reacts with at least one novel antibody, and there is good accompanying molecular data. Monoclonal antibodies to surface CD antigens on leukocytes have been used for flow cytometry, and more recently to construct microarrays that capture live cells. These DotScan microarrays enable the rapid and highly parallel characterization of repertoires of CD antigens whose expression patterns may be correlated with discrete leukaemia subtypes, or used to define biomarker 'signatures' for non-hematological diseases. DotScan with fluorescence multiplexing enables profiling of CD antigens for minor subsets of cells, such as colorectal cancer cells and tumour-infiltrating lymphocytes from a surgical sample.

Human neutrophil-expressed CD28 interacts with macrophage B7 to induce phosphatidylinositol 3-kinase-dependent IFN-gamma secretion and restriction of Leishmania growth

We previously showed that CD28 is expressed on human peripheral blood neutrophils and plays an important role in CXCR-1 expression and IL-8-induced neutrophil migration. In this work we demonstrate that Leishmania major infection of macrophages results in parasite dose-dependent IL-8 secretion in vitro and in IL-8-directed neutrophil migration, as blocked by both anti-IL-8 and anti-IL-8R Abs, toward the L. major-infected macrophages. In the neutrophil-macrophage cocultures, both CTLA4-Ig, a fusion protein that blocks CD28-CD80/CD86 interaction, and a neutralizing anti-IFN-gamma Ab inhibit the anti-leishmanial function of neutrophils, suggesting that the neutrophil-macrophage interaction via CD28-CD80/CD86 plays an important role in the IFN-gamma-dependent restriction of the parasite growth. Cross-linking of neutrophil-expressed CD28 by monoclonal anti-CD28 Ab or B7.1-Ig or B7.2-Ig results in phosphatidylinositol 3-kinase association with CD28 and in wortmannin-sensitive but cyclosporin A-resistant induction and secretion of IFN-gamma. Whereas the neutrophils secrete IFN-gamma with CD28 signal alone, the T cells do not secrete the cytokine in detectable amounts with the same signal. Thus, neutrophil-expressed CD28 modulates not only the granulocyte migration but also induction and secretion of IFN-gamma at the site of infection where it migrates from the circulation.

Cellular pathology changes in rat skin following intradermal injection of nerve growth factor: neutrophil-dependent and -independent events

Nerve growth factor (NGF) regulates the survival and development of specific populations of neurones and is involved in wound healing. A further area of study relating to the role of neurotrophins in the mature animal has concerned the possibility that NGF may be a pivotal mediator of inflammation and pain. It has previously been shown that injection of intradermal NGF can result in a neutrophil-dependent hyperalgesia in the rat. The purpose of the present study was to examine the pathological consequence of NGF injected intradermally into mature rat skin and to examine further the role of neutrophils. Standard histopathology techniques (H & E) were employed to determine inflammatory cell counts. Circulating neutrophils were depleted using an anti-rat neutrophil antiserum and results were compared to treatment with vehicle controls. Saline-pretreated rats exhibited normal circulating neutrophil numbers and the dorsal skin showed a significant increase of neutrophil and macrophages at 3 and 5 h and lymphocytes at 5 h after NGF treatment. By comparison, skin sites from neutrophil-depleted rats did not demonstrate a significant increase in neutrophil and macrophage accumulation after NGF administration. All NGF-treated sites, independent of pretreatment, demonstrated abnormal muscle fibre morphology and proliferation of the muscle sarcolemmal nuclei after NGF injection, indicative of tissue injury. In addition, oedema and some fibroplasia were also noted. Furthermore, fibrin production was increased at 3 and 5 h after NGF administration. It is suggested that NGF has a damaging effect on rat muscle which is independent of accumulating neutrophil and other inflammatory cells. In conclusion, the findings indicate a link between NGF-induced neutrophil and macrophage accumulation, as the increase in dermal macrophages was not observed in neutrophil-depleted rats. The results also suggest that NGF can have a profound effect on rat muscle and that this effect may be related to muscle regeneration.