Reactive oxygen species production in the phagosome: impact on antigen presentation in dendritic cells

The phagosome and redox control of antigen processing

In addition to debris clearance and antimicrobial function, versatile organelles known as phagosomes play an essential role in the processing of exogenous antigen in antigen presenting cells. While there has been much attention on human leukocyte antigen haplotypes in the determination of antigenic peptide repertoires, the lumenal biochemistries within phagosomes and endosomes are emerging as equally-important determinants of peptide epitope composition and immunodominance. Recently, the lumenal redox microenvironment within these degradative compartments has been shown to impact two key antigenic processing chemistries: proteolysis by lysosomal cysteine proteases and disulfide reduction of protein antigens. Through manipulation of the balance between oxidative and reductive capacities in the phagosome-principally by modulating NADPH oxidase (NOX2) and γ-interferon-inducible lysosomal thiol reductase (GILT) activities-studies have demonstrated changes to antigen processing patterns leading to modified repertoires of antigenic peptides available for presentation, and subsequently, altered disease progression in T cell-driven autoimmunity. This review focuses on the mechanisms and consequences of redox-mediated phagosomal antigen processing, and the potential downstream implications to tolerance and autoimmunity.

NADPH oxidases and ROS signaling in the gastrointestinal tract

Reactive oxygen species (ROS), initially categorized as toxic by-products of aerobic metabolism, have often been called a double-edged sword. ROS are considered indispensable when host defense and redox signaling is concerned and a threat in inflammatory or degenerative diseases. This generalization does not take in account the diversity of oxygen metabolites being generated, their physicochemical characteristics and their production by distinct enzymes in space and time. NOX/DUOX NADPH oxidases are the only enzymes solely dedicated to ROS production and the prime ROS producer for intracellular and intercellular communication due to their widespread expression and intricate regulation. Here we discuss new insights of how NADPH oxidases act via ROS as multifaceted regulators of the intestinal barrier in homeostasis, infectious disease and intestinal inflammation. A closer look at monogenic VEOIBD and commensals as ROS source supports the view of H₂O₂ as key beneficial messenger in the barrier ecosystem.

Mitochondrial reactive oxygen species regulate the induction of CD8+ T cells by plasmacytoid dendritic cells

Cross-presentation allows exogenous antigen presentation in association with major histocompatibility complex class I molecules, a process crucial for the priming of CD8⁺ T-cell responses against viruses and tumors. By contrast to conventional dendritic cells (cDC), which cross-present antigens in the steady state, plasmacytoid dendritic cells (pDC) acquire this ability only after stimulation by Toll-like receptor (TLR) ligands. The intracellular pathways accounting for this functional difference are still unknown. Here we show that the induction of cross-presentation by pDCs is regulated by mitochondria through a reactive oxygen species (ROS)-dependent mechanism, involving pH alkalization and antigen protection. The reduction of mitochondrial ROS production dramatically decreases the cross-presentation capacity of pDCs, leading to a strong reduction of their capacity to trigger CD8⁺ T-cell responses. Our results demonstrate the importance of mitochondrial metabolism in pDC biology, particularly for the induction of adaptive immune responses.

Polymeric Nanocapsules for Vaccine Delivery: Influence of the Polymeric Shell on the Interaction With the Immune System

The use of biomaterials and nanosystems in antigen delivery has played a major role in the development of novel vaccine formulations in the last few decades. In an effort to gain a deeper understanding of the interactions between these systems and immunocompetent cells, we describe here a systematic in vitro and in vivo study on three types of polymeric nanocapsules (NCs). These carriers, which contained protamine (PR), polyarginine (PARG), or chitosan (CS) in the external shell, and their corresponding nanoemulsion were prepared, and their main physicochemical properties were characterized. The particles had a mean particle size in the range 250–450 nm and a positive zeta potential (~30–40 mV). The interaction of the nanosystems with different components of the immune system were investigated by measuring cellular uptake, reactive oxygen species production, activation of the complement cascade, cytokine secretion profile, and MAP kinases/nuclear factor κB activation. The results of these in vitro cell experiments showed that the NC formulations that included the arginine-rich polymers (PR and PARG) showed a superior ability to trigger different immune processes. Considering this finding, protamine and polyarginine nanocapsules (PR and PARG NCs) were selected to assess the association of the recombinant hepatitis B surface antigen (rHBsAg) as a model antigen to evaluate their ability to produce a protective immune response in mice. In this case, the results showed that PR NCs elicited higher IgG levels than PARG NCs and that this IgG response was a combination of anti-rHBsAg IgG1/IgG2a. This work highlights the potential of PR NCs for antigen delivery as an alternative to other positively charged nanocarriers.

Regulation of the Cell Biology of Antigen Cross-Presentation

Antigen cross-presentation is an adaptation of the cellular process of loading MHC-I molecules with endogenous peptides during their biosynthesis within the endoplasmic reticulum. Cross-presented peptides derive from internalized proteins, microbial pathogens, and transformed or dying cells. The physical separation of internalized cargo from the endoplasmic reticulum, where the machinery for assembling peptide-MHC-I complexes resides, poses a challenge. To solve this problem, deliberate rewiring of organelle communication within cells is necessary to prepare for cross-presentation, and different endocytic receptors and vesicular traffic patterns customize the emergent cross-presentation compartment to the nature of the peptide source. Three distinct pathways of vesicular traffic converge to form the ideal cross-presentation compartment, each regulated differently to supply a unique component that enables cross-presentation of a diverse repertoire of peptides. Delivery of centerpiece MHC-I molecules is the critical step regulated by microbe-sensitive Toll-like receptors. Defining the subcellular sources of MHC-I and identifying sites of peptide loading during cross-presentation remain key challenges.

Moesin and myosin IIA modulate phagolysosomal biogenesis in macrophages

Biogenesis of phagolysosomes is central to the elimination of pathogens by macrophages. We previously showed that Src homology region 2 domain-containing phosphatase 1 (SHP-1) participates in the regulation of phagosome maturation. Through proteomics, we identified moesin and the non-muscle myosin-IIA as proteins interacting with SHP-1 during phagocytosis. Silencing of either moesin or myosin IIA with small interfering RNA inhibited phagosomal acidification and recruitment of LAMP-1. Moreover, the intraphagosomal oxidative burst was impaired in the absence of either SHP-1 or myosin IIA but not moesin. Finally, absence of either SHP-1, moesin, or myosin IIA ablated the capacity of macrophages to clear bacterial infection. Collectively, these results implicate both moesin and myosin IIA in the regulation of phagolysosome biogenesis and in host defense against infections.

STIM1 promotes migration, phagosomal maturation and antigen cross-presentation in dendritic cells

Antigen cross-presentation by dendritic cells (DC) stimulates cytotoxic T cell activation to promote immunity to intracellular pathogens, viruses and cancer. Phagocytosed antigens generate potent T cell responses, but the signalling and trafficking pathways regulating their cross-presentation are unclear. Here, we show that ablation of the store-operated-Ca²⁺-entry regulator STIM1 in mouse myeloid cells impairs cross-presentation and DC migration in vivo and in vitro. Stim1 ablation reduces Ca²⁺ signals, cross-presentation, and chemotaxis in mouse bone-marrow-derived DCs without altering cell differentiation, maturation or phagocytic capacity. Phagosomal pH homoeostasis and ROS production are unaffected by STIM1 deficiency, but phagosomal proteolysis and leucyl aminopeptidase activity, IRAP recruitment, as well as fusion of phagosomes with endosomes and lysosomes are all impaired. These data suggest that STIM1-dependent Ca²⁺ signalling promotes the delivery of endolysosomal enzymes to phagosomes to enable efficient cross-presentation.

STIM proteins sense Ca²⁺ depletion in the ER and activate store-operated Ca²⁺-entry (SOCE) in response, a process associated with dendritic cell functions. Here the authors show STIM1 is the major isoform controlling SOCE in mouse dendritic cells and provide a mechanism for its requirement in antigen cross-presentation.

Perivascular adipose tissue inflammation in vascular disease

Perivascular adipose tissue (PVAT) plays a critical role in the pathogenesis of cardiovascular disease. In vascular pathologies, perivascular adipose tissue increases in volume and becomes dysfunctional, with altered cellular composition and molecular characteristics. PVAT dysfunction is characterized by its inflammatory character, oxidative stress, diminished production of vaso-protective adipocyte-derived relaxing factors and increased production of paracrine factors such as resistin, leptin, cytokines (IL-6 and TNF-α) and chemokines [RANTES (CCL5) and MCP-1 (CCL2)]. These adipocyte-derived factors initiate and orchestrate inflammatory cell infiltration including primarily T cells, macrophages, dendritic cells, B cells and NK cells. Protective factors such as adiponectin can reduce NADPH oxidase superoxide production and increase NO bioavailability in the vessel wall, while inflammation (e.g. IFN-γ or IL-17) induces vascular oxidases and eNOS dysfunction in the endothelium, vascular smooth muscle cells and adventitial fibroblasts. All of these events link the dysfunctional perivascular fat to vascular dysfunction. These mechanisms are important in the context of a number of cardiovascular disorders including atherosclerosis, hypertension, diabetes and obesity. Inflammatory changes in PVAT's molecular and cellular responses are uniquely different from classical visceral or subcutaneous adipose tissue or from adventitia, emphasizing the unique structural and functional features of this adipose tissue compartment. Therefore, it is essential to develop techniques for monitoring the characteristics of PVAT and assessing its inflammation. This will lead to a better understanding of the early stages of vascular pathologies and the development of new therapeutic strategies focusing on perivascular adipose tissue.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Tumor-Derived Microvesicles Modulate Antigen Cross-Processing via Reactive Oxygen Species-Mediated Alkalinization of Phagosomal Compartment in Dendritic Cells

Dendritic cells (DCs) are the only antigen-presenting cells able to prime naïve T cells and cross-prime antigen-specific CD8⁺ T cells. Their functionality is a requirement for the induction and maintenance of long-lasting cancer immunity. Albeit intensively investigated, the in vivo mechanisms underlying efficient antigen cross-processing and presentation are not fully understood. Several pieces of evidence indicate that antigen transfer to DCs mediated by microvesicles (MVs) enhances antigen immunogenicity. This mechanism is also relevant for cross-presentation of those tumor-associated glycoproteins such as MUC1 that are blocked in HLA class II compartment when internalized by DCs as soluble molecules. Here, we present pieces of evidence that the internalization of tumor-derived MVs modulates antigen-processing machinery of DCs. Employing MVs derived from ovarian cancer ascites fluid and established tumor cell lines, we show that MV uptake modifies DC phagosomal microenvironment, triggering reactive oxygen species (ROS) accumulation and early alkalinization. Indeed, tumor MVs carry radical species and the MV uptake by DCs counteracts the chemically mediated acidification of the phagosomal compartment. Further pieces of evidence suggest that efficacious antigen cross-priming of the MUC1 antigen carried by the tumor MVs results from the early signaling induced by MV internalization and the function of the antigen-processing machinery of DCs. These results strongly support the hypothesis that tumor-derived MVs impact antigen immunogenicity by tuning the antigen-processing machinery of DCs, besides being carrier of tumor antigens. Furthermore, these findings have important implications for the exploitation of MVs as antigenic cell-free immunogen for DC-based therapeutic strategies.

Dendritic cell maturation and cross-presentation: timing matters!

As a population, dendritic cells (DCs) appear to be the best cross‐presenters of internalized antigens on major histocompatibility complex class I molecules in the mouse. To do this, DCs have developed a number of unique and dedicated means to control their endocytic and phagocytic pathways: among them, the capacity to limit acidification of their phagosomes, to prevent proteolytic degradation, to delay fusion of phagosomes to lysosomes, to recruit ER proteins to phagosomes, and to export phagocytosed antigens to the cytosol. The regulation of phagocytic functions, and thereby of antigen processing and presentation by innate signaling, represents a critical level of integration of adaptive and innate immune responses. Understanding how innate signals control antigen cross‐presentation is critical to define effective vaccination strategies for CD8⁺ T‐cell responses.

VAMP8-mediated NOX2 recruitment to endosomes is necessary for antigen release

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DAP is more profitable in climbing bean-rotation than in bush bean-maize rotation.

Cross-presentation of foreign antigen in major histocompatibility complex (MHC) class I by dendritic cells (DCs) requires activation of the NADPH-oxidase NOX2 complex. We recently showed that NOX2 is recruited to phagosomes by the SNARE protein VAMP8 where NOX2-produced reactive oxygen species (ROS) cause lipid oxidation and membrane disruption, promoting antigen translocation into the cytosol for cross-presentation. In this study, we extend these findings by showing that VAMP8 is also involved in NOX2 trafficking to endosomes. Moreover, we demonstrate in both human and mouse DCs that absence of VAMP8 leads to decreased ROS production, lipid peroxidation and antigen translocation, and that this impairs cross-presentation. In contrast, knockdown of VAMP8 did not affect recruitment of MHC class I and the transporter associated with antigen processing 1 (TAP1) to phagosomes, although surface levels of MHC class I were reduced. Thus, in addition to a secretory role, VAMP8-mediates trafficking of NOX2 to endosomes and phagosomes and this promotes induction of cytolytic T cell immune responses.

The ER phagosome connection in the era of membrane contact sites

Phagocytosis is an essential mechanism through which innate immune cells ingest foreign material that is either destroyed or used to generate and present antigens and initiate adaptive immune responses. While a role for the ER during phagosome biogenesis has been recognized, whether fusion with ER cisternae or vesicular derivatives occurs has been the source of much contention. Membrane contact sites (MCS) are tight appositions between ER membranes and various organelles that coordinate multiple functions including localized signalling, lipid transfer and trafficking. The discovery that MCS form between the ER and phagosomes now begs the question of whether MCS play a role in connecting the ER to phagosomes under different contexts. In this review, we consider the implications of MCS between the ER and phagosomes during cross-presentation and infection with intracellular pathogens. We also discuss the similarities between these contacts and those between the ER and plasma membrane and acidic organelles such as endosomes and lysosomes. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann.

Role of Protein Kinase C and Nox2-Derived Reactive Oxygen Species Formation in the Activation and Maturation of Dendritic Cells by Phorbol Ester and Lipopolysaccharide

Aims. Activation/maturation of dendritic cells (DCs) plays a central role in adaptive immune responses by antigen processing and (cross-) activation of T cells. There is ongoing discussion on the role of reactive oxygen species (ROS) in these processes and with the present study we investigated this enigmatic pathway. Methods and Results. DCs were cultured from precursors in the bone marrow of mice (BM-DCs) and analyzed for ROS formation, maturation, and T cell stimulatory capacity upon stimulation with phorbol ester (PDBu) and lipopolysaccharide (LPS). LPS stimulation of BM-DCs caused maturation with moderate intracellular ROS formation, whereas PDBu treatment resulted in maturation with significant ROS formation. The NADPH oxidase inhibitors apocynin/VAS2870 and genetic gp91phox deletion both decreased the ROS signal in PDBu-stimulated BM-DCs without affecting maturation and T cell stimulatory capacity of BM-DCs. In contrast, the protein kinase C inhibitors chelerythrine/Gö6983 decreased PDBu-stimulated ROS formation in BM-DCs as well as maturation. Conclusion. Obviously Nox2-dependent ROS formation in BM-DCs is not always required for their maturation or T cell stimulatory potential. PDBu/LPS-triggered BM-DC maturation rather relies on phosphorylation cascades. Our results question the role of oxidative stress as an essential “danger signal” for BM-DC activation, although we cannot exclude contribution by other ROS sources.

Novel Immune Mechanisms in Hypertension and Cardiovascular Risk

PURPOSE OF REVIEW

Hypertension is a common disorder with substantial impact on public health due to highly elevated cardiovascular risk. The mechanisms still remain unclear and treatments are not sufficient to reduce risk in majority of patients. Inflammatory mechanisms may provide an important mechanism linking hypertension and cardiovascular risk. We aim to review newly identified immune and inflammatory mechanisms of hypertension with focus on their potential therapeutic impact.

RECENT FINDINGS

In addition to the established role of the vasculature, kidneys and central nervous system in pathogenesis of hypertension, low-grade inflammation contributes to this disorder as indicated by experimental models and GWAS studies pointing to SH2B3 immune gene as top key driver of hypertension. Immune responses in hypertension are greatly driven by neoantigens generated by oxidative stress and modulated by chemokines such as RANTES, IP-10 and microRNAs including miR-21 and miR-155 with other molecules under investigation. Cells of both innate and adoptive immune system infiltrate vasculature and kidneys, affecting their function by releasing pro-inflammatory mediators and reactive oxygen species.

SUMMARY

Immune and inflammatory mechanisms of hypertension provide a link between high blood pressure and increased cardiovascular risk, and reduction of blood pressure without attention to these underlying mechanisms is not sufficient to reduce risk.

The Optimization of Bioorthogonal Epitope Ligation within MHC-I Complexes

Antigen recognition followed by the activation of cytotoxic T-cells (CTLs) is a key step in adaptive immunity, resulting in clearance of viruses and cancers. The repertoire of peptides that have the ability to bind to the major histocompatibility type-I (MHC-I) is enormous, but the approaches available for studying the diversity of the peptide repertoire on a cell are limited. Here, we explore the use of bioorthogonal chemistry to quantify specific peptide-MHC-I complexes (pMHC-I) on cells. We show that modifying epitope peptides with bioorthogonal groups in surface accessible positions allows wild-type-like MHC-I binding and bioorthogonal ligation using fluorogenic chromophores in combination with a Cu(I)-catalyzed Huisgen cycloaddition reaction. We expect that this approach will make a powerful addition to the antigen presentation toolkit as for the first time it allows quantification of antigenic peptides for which no detection tools exist.

Saponin-based adjuvants induce cross-presentation in dendritic cells by intracellular lipid body formation

Saponin-based adjuvants (SBAs) are being used in animal and human (cancer) vaccines, as they induce protective cellular immunity. Their adjuvant potency is a factor of inflammasome activation and enhanced antigen cross-presentation by dendritic cells (DCs), but how antigen cross-presentation is induced is not clear. Here we show that SBAs uniquely induce intracellular lipid bodies (LBs) in the CD11b+ DC subset in vitro and in vivo. Using genetic and pharmacological interference in models for vaccination and in situ tumour ablation, we demonstrate that LB induction is causally related to the saponin-dependent increase in cross-presentation and T-cell activation. These findings link adjuvant activity to LB formation, aid the application of SBAs as a cancer vaccine component, and will stimulate development of new adjuvants enhancing T-cell-mediated immunity.

Saponin-based adjuvants are being explored as vaccine components as they induce high levels of antigen cross-presentation, but it is unknown how. Here the authors show that these adjuvants enhance cross-presentation by driving production of lipid bodies inside CD11b dendritic cells.

Immunoregulatory functions of immune complexes in vaccine and therapy

Clinical and experimental preparations of IgG/soluble antigen complexes, as well as those formed following antibody therapy in vivo, are multifaceted immune regulators. These immune complexes (ICs) have been tested in humans and animal models, mostly in forms of experimental or clinical vaccination, for at least a century. With intensified research on Fcγ receptor-mediated immune modulation, as well as with immune complex-directed antigen processing, presentation, and inflammatory responses, there are renewed interests of using ICs in vaccines and immunotherapies. Currently, IC-based immune therapy has been broadly experimented in HBV and HIV viral infection control and antitumor treatments. However, mechanistic insights of IC-based treatments are relatively recent subjects of study; strong efforts are needed to establish links to connect laboratory findings with clinical practices. This review covers the history, mechanisms, and in vivo outcomes of this safe and effective therapeutic tool, with a clear aim to bridge laboratory findings with evolving clinical applications.

Diverse HLA-I Peptide Repertoires of the APC Lines MUTZ3-Derived Immature and Mature Dendritic Cells and THP1-Derived Macrophages

Dendritic cells (DCs) and macrophages are specialized APCs that process and present self-Ags for induction of tolerance and foreign Ags to initiate T cell-mediated immunity. Related to differentiation states they have specific phenotypes and functions. However, the impact of these differentiations on Ag processing and presentation remains poorly defined. To gain insight into this, we analyzed and compared the HLA-I peptidomes of MUTZ3-derived human immature and mature DC lines and THP1-derived macrophages by liquid chromatography tandem mass spectrometry. We found that the HLA-I peptidomes were heterogeneous and individualized and were dominated by nonapeptides with similar HLA-I binding affinities and anchor residues. MUTZ3-derived DCs and THP1-derived macrophages were able to sample peptides from source proteins of almost all subcellular locations and were involved in various cellular functions in similar proportion, with preference to proteins involved in cell communication, signal transduction, protein metabolism, and transcription factor/regulator activity.

New "light" for one-world approach toward safe and effective control of animal diseases and insect vectors from leishmaniac perspectives

Light is known to excite photosensitizers (PS) to produce cytotoxic reactive oxygen species (ROS) in the presence of oxygen. This modality is attractive for designing control measures against animal diseases and pests. Many PS have a proven safety record. Also, the ROS cytotoxicity selects no resistant mutants, unlike other drugs and pesticides. Photodynamic therapy (PDT) refers to the use of PS as light activable tumoricides, microbicides and pesticides in medicine and agriculture.

Here we describe “photodynamic vaccination” (PDV) that uses PDT-inactivation of parasites, i.e. Leishmania as whole-cell vaccines against leishmaniasis, and as a universal carrier to deliver transgenic add-on vaccines against other infectious and malignant diseases. The efficacy of Leishmania for vaccine delivery makes use of their inherent attributes to parasitize antigen (vaccine)-presenting cells. Inactivation of Leishmania by PDT provides safety for their use. This is accomplished in two different ways: (i) chemical engineering of PS to enhance their uptake, e.g. Si-phthalocyanines; and (ii) transgenic approach to render Leishmania inducible for porphyrinogenesis. Three different schemes of Leishmania-based PDV are presented diagrammatically to depict the cellular events resulting in cell-mediated immunity, as seen experimentally against leishmaniasis and Leishmania-delivered antigen in vitro and in vivo. Safety versus efficacy evaluations are under way for PDT-inactivated Leishmania, including those further processed to facilitate their storage and transport. Leishmania transfected to express cancer and viral vaccine candidates are being prepared accordingly for experimental trials.

We have begun to examine PS-mediated photodynamic insecticides (PDI). Mosquito cells take up rose bengal/cyanosine, rendering them light-sensitive to undergo disintegration in vitro, thereby providing a cellular basis for the larvicidal activity seen by the same treatments. Ineffectiveness of phthalocyanines and porphyrins for PDI underscores its requirement for different PS. Differential uptake of PS by insect versus other cells to account for this difference is under study.

The ongoing work is patterned after the one-world approach by enlisting the participation of experts in medicinal chemistry, cell/molecular biology, immunology, parasitology, entomology, cancer research, tropical medicine and veterinary medicine. The availability of multidisciplinary expertise is indispensable for implementation of the necessary studies to move the project toward product development.

Lipid peroxidation causes endosomal antigen release for cross-presentation

Dendritic cells (DCs) present foreign antigen in major histocompatibility complex (MHC) class I molecules to cytotoxic T cells in a process called cross-presentation. An important step in this process is the release of antigen from the lumen of endosomes into the cytosol, but the mechanism of this step is still unclear. In this study, we show that reactive oxygen species (ROS) produced by the NADPH-oxidase complex NOX2 cause lipid peroxidation, a membrane disrupting chain-reaction, which in turn results in antigen leakage from endosomes. Antigen leakage and cross-presentation were inhibited by blocking ROS production or scavenging radicals and induced when using a ROS-generating photosensitizer. Endosomal antigen release was impaired in DCs from chronic granulomatous disease (CGD) patients with dysfunctional NOX2. Thus, NOX2 induces antigen release from endosomes for cross-presentation by direct oxidation of endosomal lipids. This constitutes a new cellular function for ROS in regulating immune responses against pathogens and cancer.

Endogenous and exogenous pathways maintain the reductive capacity of the phagosome

Although endosomes, lysosomes, and phagosomes require a reductive environment for the optimal activity of disulfide reductases and other thiol-dependent enzymes, how these reductive environments are established and maintained remain unknown. Our goal in this study was to begin to elucidate the redox control systems responsible for maintaining redox-sensitive enzymatic activities in the phagolysosome of murine macrophages. Through the use of specific inhibitors and genetic knockdown of known redox enzymes, we identified redox pathways that influence phagosomal disulfide reduction. In particular, known inhibitors of the NADPH-dependent selenoprotein, thioredoxin reductase, were shown to inhibit phagosomal disulfide reduction and phagosomal proteolysis. This was supported by the observation that conditional deletion of the selenocysteine tRNA in macrophages decreased phagosomal disulfide reduction capacity. In addition, pharmacologic inhibition of the pentose phosphate pathway decreased rates of disulfide reduction and proteolysis in the phagosome, implicating NADPH as a source of phagosomal reductive energy. Finally, by analyzing the effect of extracellular redox couples, such as cysteine:cystine on thiol-dependent phagosomal processes, we demonstrated that the extracellular space can additionally supply the phagosome with reductive energy. Collectively, these data demonstrate that defined cytosolic reductive pathways act in concert with the uptake of cysteine from the extracellular space to support thiol-dependent chemistries in the phagosome.

Measuring Phagosome pH by Ratiometric Fluorescence Microscopy

Phagocytosis is a fundamental process through which innate immune cells engulf bacteria, apoptotic cells or other foreign particles in order to kill or neutralize the ingested material, or to present it as antigens and initiate adaptive immune responses. The pH of phagosomes is a critical parameter regulating fission or fusion with endomembranes and activation of proteolytic enzymes, events that allow the phagocytic vacuole to mature into a degradative organelle. In addition, translocation of H(+) is required for the production of high levels of reactive oxygen species (ROS), which are essential for efficient killing and signaling to other host tissues. Many intracellular pathogens subvert phagocytic killing by limiting phagosomal acidification, highlighting the importance of pH in phagosome biology. Here we describe a ratiometric method for measuring phagosomal pH in neutrophils using fluorescein isothiocyanate (FITC)-labeled zymosan as phagocytic targets, and live-cell imaging. The assay is based on the fluorescence properties of FITC, which is quenched by acidic pH when excited at 490 nm but not when excited at 440 nm, allowing quantification of a pH-dependent ratio, rather than absolute fluorescence, of a single dye. A detailed protocol for performing in situ dye calibration and conversion of ratio to real pH values is also provided. Single-dye ratiometric methods are generally considered superior to single wavelength or dual-dye pseudo-ratiometric protocols, as they are less sensitive to perturbations such as bleaching, focus changes, laser variations, and uneven labeling, which distort the measured signal. This method can be easily modified to measure pH in other phagocytic cell types, and zymosan can be replaced by any other amine-containing particle, from inert beads to living microorganisms. Finally, this method can be adapted to make use of other fluorescent probes sensitive to different pH ranges or other phagosomal activities, making it a generalized protocol for the functional imaging of phagosomes.

Trypanosoma cruzi extracts elicit protective immune response against chemically induced colon and mammary cancers

Trypanosoma cruzi, the protozoan parasite that causes Chagas' disease, has anticancer effects mediated, at least in part, by parasite-derived products which inhibit growth of tumor cells. We investigated whether immunity to T. cruzi antigens could induce antitumor activity, using two rat models which reproduce human carcinogenesis: colon cancer induced by 1,2-dimethylhydrazine (DMH), and mammary cancer induced by N-nitroso-N-methylurea (NMU). We found that vaccination with T. cruzi epimastigote lysates strongly inhibits tumor development in both animal models. Rats immunized with T. cruzi antigens induce activation of both CD4(+) and CD8(+) T cells and splenocytes from these animals showed higher cytotoxic responses against tumors as compared to rats receiving adjuvant alone. Tumor-associated immune responses included increasing number of CD11b/c(+) His48(-) MHC II(+) cells corresponding to macrophages and/or dendritic cells, which exhibited augmented NADPH-oxidase activity. We also found that T. cruzi lysate vaccination developed antibodies specific for colon and mammary rat cancer cells, which were capable of mediating antibody-dependent cellular cytotoxicity (ADCC) in vitro. Anti-T. cruzi antibodies cross-reacted with human colon and breast cancer cell lines and recognized 41/60 (68%) colon cancer and 38/63 (60%) breast cancer samples in a series of 123 human tumors. Our results suggest that T. cruzi antigens can evoke an integrated antitumor response involving both the cellular and humoral components of the immune response and provide novel insights into the understanding of the intricate relationship between parasite infection and tumor growth.

NOX2 As a Target for Drug Development: Indications, Possible Complications, and Progress

SIGNIFICANCE

NOX2 is important for host defense, and yet is implicated in a large number of diseases in which inflammation plays a role in pathogenesis. These include acute and chronic lung inflammatory diseases, stroke, traumatic brain injury, and neurodegenerative diseases, including Alzheimer's and Parkinson's Diseases.

RECENT ADVANCES

Recent drug development programs have targeted several NOX isoforms that are implicated in a variety of diseases. The focus has been primarily on NOX4 and NOX1 rather than on NOX2, due, in part, to concerns about possible immunosuppressive side effects. Nevertheless, NOX2 clearly contributes to the pathogenesis of many inflammatory diseases, and its inhibition is predicted to provide a novel therapeutic approach.

CRITICAL ISSUES

Possible side effects that might arise from targeting NOX2 are discussed, including the possibility that such inhibition will contribute to increased infections and/or autoimmune disorders. The state of the field with regard to existing NOX2 inhibitors and targeted development of novel inhibitors is also summarized.

FUTURE DIRECTIONS

NOX2 inhibitors show particular promise for the treatment of inflammatory diseases, both acute and chronic. Theoretical side effects include pro-inflammatory and autoimmune complications and should be considered in any therapeutic program, but in our opinion, available data do not indicate that they are sufficiently likely to eliminate NOX2 as a drug target, particularly when weighed against the seriousness of many NOX2-related indications. Model studies demonstrating efficacy with minimal side effects are needed to encourage future development of NOX2 inhibitors as therapeutic agents.

Pharmacological Potential of NOX2 Agonists in Inflammatory Conditions

SIGNIFICANCE

New insights into the role of reactive oxygen species (ROS) show that activators of the phagocyte NADPH oxidase 2 (NOX2) complex have the potential to be therapeutic in autoimmune and inflammatory conditions. It is, however, essential to elucidate the consequence of targeting the NOX2 complex, as it might lead to different outcomes depending on disease context and specificity, dose, and timing of ROS production.

RECENT ADVANCES

Increasing evidence is suggesting that the role of the NOX2 complex is far more complex than previously anticipated. In addition to the well-described antimicrobial response, ROS also have immune and inflammatory regulatory effects. Compounds increasing NOX2-dependent ROS production have been shown to be effective both in preventing and in treating inflammatory manifestations in animal models of autoimmune diseases. Altogether, these results suggest the possibility of activating the NOX2 complex for the treatment of autoimmune inflammatory diseases while restoring and maintaining a balanced ROS regulation.

CRITICAL ISSUES

The complexity of the NOX system and the derived ROS is important and must be considered when designing the programs for the development of NOX2-activating drugs, as well as for validation of selected hits, to successfully identify substances effective in treating inflammatory and autoimmune conditions. In addition, it is important to consider the complex downstream immunological effects and safety for drugs that increase the production of ROS.

FUTURE DIRECTIONS

There is a strong potential for the development of ROS-inducing drugs, targeting the NOX2 complex, which are effective and safe, for the treatment of inflammatory autoimmune disorders. In such drug development, one must carefully investigate the pharmaceutical properties, including both efficacy and safety of the drugs. In addition, the immunological pathways of this new treatment strategy need careful examination.

Mitochondrial reactive oxygen species modulate innate immune response to influenza A virus in human nasal epithelium

The innate immune system of the nasal epithelium serves as a first line of defense against invading respiratory viruses including influenza A virus (IAV). Recently, it was verified that interferon (IFN)-related immune responses play a critical role in local antiviral innate immunity. Reactive oxygen species (ROS) generation by exogenous pathogens has also been demonstrated in respiratory epithelial cells and modulation of ROS has been reported to be important for respiratory virus-induced innate immune mechanisms. Passage-2 normal human nasal epithelial (NHNE) cells were inoculated with IAV (WS/33, H1N1) to assess the sources of IAV-induced ROS and the relationship between ROS and IFN-related innate immune responses. Both STAT1 and STAT2 phosphorylation and the mRNA levels of IFN-stimulated genes, including Mx1, 2,5-OAS1, IFIT1, and CXCL10, were induced after IAV infection up to three days post infection. Similarly, we observed that mitochondrial ROS generation increased maximally at 2 days after IAV infection. After suppression of mitochondrial ROS generation, IAV-induced phosphorylation of STAT and mRNA levels of IFN-stimulated genes were attenuated and actually, viral titers of IAV were significantly higher in cases with scavenging ROS. Our findings suggest that mitochondrial ROS might be responsible for controlling IAV infection and may be potential sources of ROS generation, which is required to initiate an innate immune response in NHNE cells.

Reactive oxygen species-mediated bacterial killing by B lymphocytes

Regulated production of ROS is mainly attributed to Nox family enzymes. In neutrophil granulocytes and macrophages, Nox2 has a crucial role in bacterial killing, and the absence of phagocytic ROS production leads to the development of CGD. Expression of Nox2 was also described in B lymphocytes, where the role of the enzyme is still poorly understood. Here, we show that peritoneal B cells, which were shown recently to possess phagocytic activity, have a high capacity to produce ROS in a Nox2-dependent manner. In phagocytosing B cells, intense intraphagosomal ROS production is detected. Finally, by studying 2 animal models of CGD, we demonstrate that phagocyte oxidase-deficient B cells have a reduced capacity to kill bacteria. Our observations extend the number of immune cell types that produce ROS to kill pathogens.

Functional manipulation of dendritic cells by photoswitchable generation of intracellular reactive oxygen species

Reactive oxygen species (ROS) play an important role in cellular signaling as second messengers. However, studying the role of ROS in physiological redox signaling has been hampered by technical difficulties in controlling their generation within cells. Here, we utilize two inert components, a photosensitizer and light, to finely manipulate the generation of intracellular ROS and examine their specific role in activating dendritic cells (DCs). Photoswitchable generation of intracellular ROS rapidly induced cytosolic mobilization of Ca(2+), differential activation of mitogen-activated protein kinases, and nuclear translocation of NF-κB. Moreover, a transient intracellular ROS surge could activate immature DCs to mature and potently enhance migration in vitro and in vivo. Finally, we observed that intracellular ROS-stimulated DCs enhanced antigen specific T-cell responses in vitro and in vivo, which led to delayed tumor growth and prolonged survival of tumor-bearing mice when immunized with a specific tumor antigen. Therefore, a transient intracellular ROS surge alone, if properly manipulated, can cause immature DCs to differentiate into a motile state and mature forms that are sufficient to initiate adaptive T cell responses in vivo.

Dendritic cells induce Th2-mediated airway inflammatory responses to house dust mite via DNA-dependent protein kinase

DNA-dependent protein kinase (DNA-PK) mediates double-stranded DNA break repair, V(D)J recombination and immunoglobulin class switch recombination, as well as innate immune and pro-inflammatory responses. However, there is limited information regarding the role of DNA-PK in adaptive immunity mediated by dendritic cells (DCs), which are the primary antigen-presenting cells in allergic asthma. Here we show that house dust mite induces DNA-PK phosphorylation, which is a marker of DNA-PK activation, in DCs via the generation of intracellular reactive oxygen species. We also demonstrate that pharmacological inhibition of DNA-PK, as well as the specific deletion of DNA-PK in DCs, attenuates the induction of allergic sensitization and Th2 immunity via a mechanism that involves the impaired presentation of mite antigens. Furthermore, pharmacological inhibition of DNA-PK following antigen priming similarly reduces the manifestations of mite-induced airway disease. Collectively, these findings suggest that DNA-PK may be a potential target for treatment of allergic asthma.

P47phox-/- mice are compromised in expansion and activation of CD8+ T cells and susceptible to Trypanosoma cruzi infection

Macrophage activation of NAD(P)H oxidase (NOX2) and reactive oxygen species (ROS) is suggested to kill Trypanosoma cruzi that causes Chagas disease. However, the role of NOX2 in generation of protective immunity and whether these mechanisms are deregulated in the event of NOX2 deficiency are not known, and examined in this study. Our data showed that C57BL/6 p47(phox-/-) mice (lack NOX2 activity), as compared to wild-type (WT) mice, succumbed within 30 days post-infection (pi) to low doses of T. cruzi and exhibited inability to control tissue parasites. P47(phox-/-) bone-marrow and splenic monocytes were not compromised in maturation, phagocytosis and parasite uptake capacity. The deficiency of NOX2 mediated ROS was compensated by higher level of inducible nitric oxide synthase (iNOS) expression, and nitric oxide and inflammatory cytokine (TNF-α, IFN-γ, IL-1β) release by p47(phox-/-) macrophages as compared to that noted in WT controls infected by T. cruzi. Splenic activation of Th1 CD4(+)T cells and tissue infiltration of immune cells in T. cruzi infected p47(phox-/-) mice were comparable to that noted in infected control mice. However, generation and activation of type 1 CD8(+)T cells was severely compromised in p47(phox-/-) mice. In comparison, WT mice exhibited a robust T. cruzi-specific CD8(+)T cell response with type 1 (IFN-γ(+)TNF-α>IL-4+IL-10), cytolytic effector (CD8(+)CD107a(+)IFN-γ(+)) phenotype. We conclude that NOX2/ROS activity in macrophages signals the development of antigen-specific CD8(+)T cell response. In the event of NOX2 deficiency, a compromised CD8(+)T cell response is generated, leading to increased parasite burden, tissue pathogenesis and mortality in chagasic mice.

γ-Interferon-inducible lysosomal thiol reductase (GILT) maintains phagosomal proteolysis in alternatively activated macrophages

Although it is known that lysosomal cysteine cathepsins require a reducing environment for optimal activity, it is not firmly established how these enzymes are maintained in their reduced-active state in the acidic and occasionally oxidative environment within phagosomes and lysosomes. γ-Interferon-inducible lysosomal thiol reductase (GILT) has been the only enzyme described in the endosomes, lysosomes, and phagosomes with the potential to catalyze the reduction of cysteine cathepsins. Our goal in the current study was to assess the effect of GILT on major phagosomal functions with an emphasis on proteolytic efficiency in murine bone marrow-derived macrophages. Assessment of phagosomal disulfide reduction upon internalization of IgG-opsonized experimental particles confirmed a major role for GILT in phagosomal disulfide reduction in both resting and interferon-γ-activated macrophages. Furthermore we observed a decrease in early phagosomal proteolytic efficiency in GILT-deficient macrophages, specifically in the absence of an NADPH oxidase-mediated respiratory burst. This deficiency was more prominent in IL-4-activated macrophages that inherently possess lower levels of NADPH oxidase activity. Finally, we provide evidence that GILT is required for optimal activity of the lysosomal cysteine protease, cathepsin S. In summary, our results suggest a role for GILT in maintaining cysteine cathepsin proteolytic efficiency in phagosomes, particularly in the absence of high NADPH oxidase activity, which is characteristic of alternatively activated macrophages.

Endo-lysosomal proteases in antigen presentation

Endo-lysosomal proteases have long been attractive, yet elusive, targets for medicinal chemistry. They have found to play key roles in health and disease; with protease under- and over-activity having been implicated in cancer, osteoporosis and Alzheimer's disease. Here we will discuss their role in the adaptive immune response. The crucial roles of these enzymes multiple processes in antigen presentation will be discussed: from activating MHC-II receptors, to the production of epitopes from antigens and the activation of Toll-like receptors. The early efforts at pharmacological interventions in these pathways will also be discussed.

Glycosaminoglycan degradation by selected reactive oxygen species

SIGNIFICANCE

Inflammatory diseases (such as arthritis) of the extracellular matrix (ECM) are of considerable socioeconomic significance. There is clear evidence that reactive oxygen species (ROS) and nitrogen species released by, for instance, neutrophils contribute to the degradation of the ECM. Here we will focus on the ROS-induced degradation of the glycosaminoglycans, one important component of the ECM.

RECENT ADVANCES

The recently developed "anti-TNF-α" therapy is primarily directed against neutrophilic granulocytes that are powerful sources of ROS. Therefore, a more detailed look into the mechanisms of the reactions of these ROS is reasonable.

CRITICAL ISSUES

Since both enzymes and ROS contribute to the pathogenesis of inflammatory diseases, it is very difficult to estimate the contributions of the individual species in a complex biological environment. This particularly applies as many products are not stable but only transient products that decompose in a time-dependent manner. Thus, the development of suitable analytical methods as well as the establishment of useful biomarkers is a challenging aspect.

FUTURE DIRECTIONS

If the mechanisms of ECM destruction are understood in more detail, then the development of suitable drugs to treat inflammatory diseases will be hopefully much more successful.

Relationship between redox status and cell fate in immunity and autoimmunity

SIGNIFICANCE

The signaling function of redox molecules is essential for an efficient and proper execution of a large number of cellular processes, contributing to the maintenance of cell homeostasis. Excessive oxidative stress is considered as playing an important role in the pathogenesis of autoimmune diseases by enhancing inflammation and breaking down the immunological tolerance through protein structural modifications that induce the appearance of neo/cryptic epitopes.

RECENT ADVANCES

There is a complex reciprocal relationship between oxidative stress and both apoptosis and autophagy, which is essential to determine cell fate. This is especially relevant in the context of autoimmune disorders in which apoptosis and autophagy play a crucial pathogenic role.

CRITICAL ISSUES

In this review, we describe the latest developments with regard to the involvement of redox molecules in the initiation and progression of autoimmune disorders, focusing on their role in cell fate regulation. We also discuss new therapeutic approaches that target oxidative stress in the treatment of these disorders. The administration of antioxidants is scarcely studied in autoimmunity, and future analyses are needed to assess its beneficial effects in preventing or ameliorating these diseases.

FUTURE DIRECTIONS

Deciphering the intricate relationships between oxidative stress and both apoptosis and autophagy in the context of autoimmunity could be critical in elucidating key pathogenic mechanisms and could lead to novel interventions for the clinical management of autoimmune diseases.

Dectin-1-dependent LC3 recruitment to phagosomes enhances fungicidal activity in macrophages

Autophagy has been postulated to play role in mammalian host defense against fungal pathogens, although the molecular details remain unclear. Here, we show that primary macrophages deficient in the autophagic factor LC3 demonstrate diminished fungicidal activity but increased cytokine production in response to Candida albicans stimulation. LC3 recruitment to fungal phagosomes requires activation of the fungal pattern receptor dectin-1. LC3 recruitment to the phagosome also requires Syk signaling but is independent of all activity by Toll-like receptors and does not require the presence of the adaptor protein Card9. We further demonstrate that reactive oxygen species generation by NADPH oxidase is required for LC3 recruitment to the fungal phagosome. These observations directly link LC3 to the inflammatory pathway against C. albicans in macrophages.

Proinflammatory cytokines differentially regulate adipocyte mitochondrial metabolism, oxidative stress, and dynamics

Proinflammatory cytokines differentially regulate adipocyte mitochondrial metabolism, oxidative stress, and dynamics. Macrophage infiltration of adipose tissue and the chronic low-grade production of inflammatory cytokines have been mechanistically linked to the development of insulin resistance, the forerunner of type 2 diabetes mellitus. In this study, we evaluated the chronic effects of TNFα, IL-6, and IL-1β on adipocyte mitochondrial metabolism and morphology using the 3T3-L1 model cell system. TNFα treatment of cultured adipocytes led to significant changes in mitochondrial bioenergetics, including increased proton leak, decreased ΔΨm, increased basal respiration, and decreased ATP turnover. In contrast, although IL-6 and IL-1β decreased maximal respiratory capacity, they had no effect on ΔΨm and varied effects on ATP turnover, proton leak, or basal respiration. Only TNFα treatment of 3T3-L1 cells led to an increase in oxidative stress (as measured by superoxide anion production and protein carbonylation) and C16 ceramide synthesis. Treatment of 3T3-L1 adipocytes with cytokines led to decreased mRNA expression of key transcription factors and control proteins implicated in mitochondrial biogenesis, including PGC-1α and eNOS as well as deceased expression of COX IV and Cyt C. Whereas each cytokine led to effects on expression of mitochondrial markers, TNFα exclusively led to mitochondrial fragmentation and decreased the total level of OPA1 while increasing OPA1 cleavage, without expression of levels of mitofusin 2, DRP-1, or mitofilin being affected. In summary, these results indicate that inflammatory cytokines have unique and specialized effects on adipocyte metabolism, but each leads to decreased mitochondrial function and a reprogramming of fat cell biology.

Are reactive oxygen species always detrimental to pathogens?

Reactive oxygen species (ROS) are deadly weapons used by phagocytes and other cell types, such as lung epithelial cells, against pathogens. ROS can kill pathogens directly by causing oxidative damage to biocompounds or indirectly by stimulating pathogen elimination by various nonoxidative mechanisms, including pattern recognition receptors signaling, autophagy, neutrophil extracellular trap formation, and T-lymphocyte responses. Thus, one should expect that the inhibition of ROS production promote infection. Increasing evidences support that in certain particular infections, antioxidants decrease and prooxidants increase pathogen burden. In this study, we review the classic infections that are controlled by ROS and the cases in which ROS appear as promoters of infection, challenging the paradigm. We discuss the possible mechanisms by which ROS could promote particular infections. These mechanisms are still not completely clear but include the metabolic effects of ROS on pathogen physiology, ROS-induced damage to the immune system, and ROS-induced activation of immune defense mechanisms that are subsequently hijacked by particular pathogens to act against more effective microbicidal mechanisms of the immune system. The effective use of antioxidants as therapeutic agents against certain infections is a realistic possibility that is beginning to be applied against viruses.

Insights into phagocytosis-coupled activation of pattern recognition receptors and inflammasomes

A decade of work shows that the core function of phagocytosis in engulfment and destruction of microorganisms is only a small facet of the full spectrum of roles for phagocytosis in the immune system. The regulation of phagocytosis and its outcomes by inflammatory pattern recognition receptors (PRRs) is now followed by new studies strengthening this concept and adding further complexity to the relationship between phagocytosis and innate immune signaling. Phagocytosis forms the platform for activation of distinct members of the Toll-like receptor family, and even dictates their signaling outcomes. In many cases, phagocytosis is a necessary precedent to the activation of cytosolic PRRs and assembly of canonical and non-canonical inflammasomes, leading to strong pro-inflammatory responses and inflammatory cell death.

Autophagic clearance of bacterial pathogens: molecular recognition of intracellular microorganisms

Autophagy is involved in several physiological and pathological processes. One of the key roles of the autophagic pathway is to participate in the first line of defense against the invasion of pathogens, as part of the innate immune response. Targeting of intracellular bacteria by the autophagic machinery, either in the cytoplasm or within vacuolar compartments, helps to control bacterial proliferation in the host cell, controlling also the spreading of the infection. In this review we will describe the means used by diverse bacterial pathogens to survive intracellularly and how they are recognized by the autophagic molecular machinery, as well as the mechanisms used to avoid autophagic clearance.

Virus interactions with endocytic pathways in macrophages and dendritic cells

Macrophages and dendritic cells (DCs) are at the front line of defence against fungi, bacteria, and viruses. Together with physical barriers, such as mucus and a range of antimicrobial compounds, they constitute a major part of the intrinsic and innate immune systems. They have elaborate features, including pattern recognition receptors (PRRs) and specialized endocytic mechanisms, cytokines and chemokines, and the ability to call on reserves. As masters of manipulation and counter-attack, viruses shunt intrinsic and innate recognition, enter immune cells, and spread from these cells throughout an organism. Here, we review mechanisms by which viruses subvert endocytic and pathogen-sensing functions of macrophages and DCs, while highlighting possible strategic advantages of infecting cells normally tuned into pathogen destruction.

Increased abscess formation and defective chemokine regulation in CREB transgenic mice

Cyclic AMP-response element-binding protein (CREB) is a transcription factor implicated in growth factor-dependent cell proliferation and survival, glucose homeostasis, spermatogenesis, circadian rhythms, and synaptic plasticity associated with memory. To study the phenotype of CREB overexpression in vivo, we generated CREB transgenic (TG) mice in which a myeloid specific hMRP8 promoter drives CREB expression. CREB TG mice developed spontaneous skin abscesses more frequently than wild type (WT) mice. To understand the role of CREB in myeloid function and innate immunity, chemokine expression in bone marrow derived macrophages (BMDMs) from CREB TG mice were compared with BMDMs from WT mice. Our results demonstrated decreased Keratinocyte-derived cytokine (KC) in CREB TG BMDMs but not TNFα protein production in response to lipid A (LPA). In addition, mRNA expression of KC and IL-1β (Interleukin)-1β was decreased in CREB TG BMDMs; however, there was no difference in the mRNA expression of TNFα, MCP-1, IL-6 and IL-12p40. The mRNA expression of IL-1RA and IL-10 was decreased in response to LPA. Nuclear factor kappa B (NFκB) expression and a subset of its target genes were upregulated in CREB TG mouse BMDMs. Although neutrophil migration was the same in both CREB TG and WT mice, Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity was significantly increased in neutrophils from CREB TG mice. Taken together, CREB overexpression in myeloid cells results in increased abscess formation in vivo and aberrant cytokine and chemokine response, and neutrophil function in vitro.