Dynamic localization of a helper NLR at the plant-pathogen interface underpins pathogen recognition

Plants employ sensor-helper pairs of NLR immune receptors to recognize pathogen effectors and activate immune responses. Yet, the subcellular localization of NLRs pre- and postactivation during pathogen infection remains poorly understood. Here, we show that NRC4, from the "NRC" solanaceous helper NLR family, undergoes dynamic changes in subcellular localization by shuttling to and from the plant-pathogen haustorium interface established during infection by the Irish potato famine pathogen Phytophthora infestans. Specifically, prior to activation, NRC4 accumulates at the extrahaustorial membrane (EHM), presumably to mediate response to perihaustorial effectors that are recognized by NRC4-dependent sensor NLRs. However, not all NLRs accumulate at the EHM, as the closely related helper NRC2 and the distantly related ZAR1 did not accumulate at the EHM. NRC4 required an intact N-terminal coiled-coil domain to accumulate at the EHM, whereas the functionally conserved MADA motif implicated in cell death activation and membrane insertion was dispensable for this process. Strikingly, a constitutively autoactive NRC4 mutant did not accumulate at the EHM and showed punctate distribution that mainly associated with the plasma membrane, suggesting that postactivation, NRC4 may undergo a conformation switch to form clusters that do not preferentially associate with the EHM. When NRC4 is activated by a sensor NLR during infection, however, NRC4 forms puncta mainly at the EHM and, to a lesser extent, at the plasma membrane. We conclude that following activation at the EHM, NRC4 may spread to other cellular membranes from its primary site of activation to trigger immune responses.

Depletion of resident alveolar macrophages does not prevent Fas-mediated lung injury in mice

Activation of the Fas/Fas ligand (FasL) system in the lungs results in a form of injury characterized by alveolar epithelial apoptosis and neutrophilic inflammation. Studies in vitro show that Fas activation induces apoptosis in alveolar epithelial cells and cytokine production in alveolar macrophages. The main goal of this study was to determine the contribution of alveolar macrophages to Fas-induced lung inflammation in mice, by depleting alveolar macrophages using clodronate-containing liposomes. Liposomes containing clodronate or PBS were instilled by intratracheal instillation. After 24 h, the mice received intratracheal instillations of the Fas-activating monoclonal antibody Jo2 or an isotype control antibody and were studied 18 h later. The Jo2 MAb induced increases in bronchoalveolar lavage fluid (BALF) total neutrophils, lung caspase-3 activity, and BALF total protein and worsened histological lung injury in the macrophage-depleted mice. Studies in vitro showed that Fas activation induced the release of the cytokine KC in a mouse lung epithelial cell line, MLE-12. These results suggest that the lung inflammatory response to Fas activation is not primarily dependent on resident alveolar macrophages and may instead depend on cytokine release by alveolar epithelial cells.

Mast cells: immunologically specific effectors and potential sources of multiple cytokines during IgE-dependent responses

Mast cells are critical effectors in many IgE-dependent responses, and the numbers and phenotype of certain mast cell populations can be influenced, through IL-3 and IL-4, by the same T cells that regulate IgE production. However, IgE can interact with cells other than mast cells, and different mast cell populations express significant variation in multiple important aspects of their phenotype, including mediator content and responses to cytokines and stimuli of activation. As a result it may be difficult to define the unique contributions of mast cells to IgE-dependent reactions. One approach for analysing the roles of various mast cell populations in individual biological responses is to attempt to elicit these reactions in mice in which the presence or absence of specific mast cell populations can be regulated experimentally. We have used genetically mast cell-deficient and mast cell-reconstituted mice to demonstrate that mast cells provide essential effector function in certain IgE-dependent responses involving the skin, stomach or lungs but are not necessary for the pulmonary alterations and death associated with active anaphylaxis. Similar approaches can be used to investigate the biological significance of the production, by mast cells stimulated with IgE and specific antigen, of cytokines similar or identical to IL-1, IL-3, IL-4, IL-5, IL-6, TNF-alpha/cachectin, IFN-gamma, GM-CSF, JE, MIP-1 alpha, MIP-1 beta and TCA3.

Cytokine balance in the lungs of patients with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) involves an intense inflammatory response in the lungs, with accumulation of both pro- and antiinflammatory cytokines in bronchoalveolar lavage fluid (BALF). Our goal was to determine how the balance between pro- and antiinflammatory mediators in the lungs changes before and after the onset of ARDS. We identified 23 patients at risk for ARDS and 46 with established ARDS and performed serial bronchoalveolar lavage (BAL). We used immunoassays to measure tumor necrosis factor alpha (TNF-alpha) and soluble TNF-alpha receptors I and II; interleukin 1 beta (IL-1 beta), IL-1 beta receptor antagonist, and soluble IL-1 receptor II; IL-6 and soluble IL-6 receptor; and IL-10. We used sensitive bioassays to measure net TNF-alpha, IL-1 beta, and IL-6 activity. Although individual cytokines increased before and after onset of ARDS, greater increases occurred in cognate receptors and/or antagonists, so that molar ratios of agonists/antagonists declined dramatically at the onset of ARDS. The molar ratios remained low for 7 d or longer, limiting the activity of soluble IL-1 beta and TNF-alpha in the lungs at the onset of ARDS. This significant antiinflammatory response early in ARDS may provide a key mechanism for limiting the net inflammatory response in the lungs.

Early pulmonary infection, inflammation, and clinical outcomes in infants with cystic fibrosis

A thorough understanding of the early natural history of cystic fibrosis (CF) lung disease is critical for the development of effective interventions in the youngest patients. We assessed the evolution of pulmonary infection, inflammation, and clinical course among 40 infants over a 2-year period through annual bronchoalveolar lavage (BAL) for culture and measurements of pro- and anti-inflammatory cytokines, semiannual infant pulmonary function testing, and quarterly clinical evaluations. Both the prevalence of CF pathogens and their density in BAL fluid increased with age. Infants had neutrophilic lower airway inflammation and elevated IL-8 concentrations independent of whether CF pathogens were recovered. Total leukocyte and neutrophil densities and IL-8 concentrations increased with density of CF pathogens in BAL fluid, whether the isolated organism was P. aeruginosa or another pathogen. IL-10 concentrations were similar in CF subjects and non-CF historical controls. Infants generally had suboptimal growth (low weight and height percentiles) and obstructive lung disease (decreased expiratory flows and air trapping). Subjects from whom CF pathogens were isolated at > 10(5) cfu/mL had the worst air trapping and lowest Brasfield chest X-ray scores. Our findings provide a foundation for future studies of early intervention in CF lung disease, including antimicrobial and anti-inflammatory therapy.

Fas/Fas ligand system mediates epithelial injury, but not pulmonary host defenses, in response to inhaled bacteria

The Fas/Fas ligand (FasL) system has been implicated in alveolar epithelial cell apoptosis during pulmonary fibrosis and acute respiratory distress syndrome. However, Fas ligation can also lead to cell activation and cytokine production. The goal of this study was to determine the role of the Fas/FasL system in host defenses against Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. We administered bacteria by aerosolization into the lungs of Fas-deficient (lpr) mice and wild-type (C57BL/6) mice and measured bacterial clearance at 6 and 12 h. One hour prior to euthanasia, the mice received an intraperitoneal injection of human serum albumin (HSA) for alveolar permeability determinations. At all times after bacterial challenges, the lungs of the lpr mice contained similar or lower numbers of bacteria than those of the C57BL/6 mice. Alveolar permeability changes, as determined by bronchoalveolar lavage fluid HSA concentrations, were less severe in the lpr mice 6 h after the challenges. In response to E. coli, the lpr mice had significantly more polymorphonuclear leukocytes (PMN) and macrophage inflammatory protein 2 in the lungs, whereas histopathologic changes were less severe. In contrast, in response to the gram-positive cocci, the lpr animals had similar or lower numbers of PMN. We conclude that the Fas/FasL system contributes to the development of permeability changes and tissue injury during-gram negative bacterial pneumonia. The Fas/FasL system did not have a major role in the clearance of aerosolized bacteria from the lungs at the bacterial doses tested.

Recombinant human Fas ligand induces alveolar epithelial cell apoptosis and lung injury in rabbits

This study investigated whether recombinant human soluble Fas ligand (rh-sFasL) induces apoptosis of primary type II pneumocytes in vitro and lung injury in vivo. Type II cells isolated from normal rabbit lung expressed Fas on their surface and became apoptotic after an 18-h incubation with rh-sFasL. Fas expression in normal rabbit lungs was localized by immunohistochemistry to alveolar and airway epithelia and alveolar macrophages. The administration of 10 microg of rh-sFasL into the right lungs of rabbits resulted 24 h later in both significantly more bronchoalveolar lavage fluid total protein and significantly more tissue changes compared with those in the left lungs, which received rh-sFasL plus Fas:Ig (a fusion protein that binds and blocks sFasL). Tissue changes included thickening of the alveolar walls, neutrophilic infiltrates, apoptotic (terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling-positive) cells in the alveolar walls, and increased expression of interleukin-8 by alveolar macrophages (as determined by immunohistochemistry). We conclude that the alveolar epithelium of normal rabbits expresses Fas and that sFasL induces lung injury and inflammation in rabbits.

Association of IL-8 and MCP-1 with the development of reexpansion pulmonary edema in rabbits

BACKGROUND

The aim of this study is to determine the relationships between the cytokines and the inflammatory response in reexpansion pulmonary edema (RPE).

METHODS

We examined the cell population, epithelial permeability measured by Evans blue dye (EB), betaglucuronidase and cytokine concentrations in bronchoalveolar lavage fluid (BALF) and/or blood using a rabbit RPE model.

RESULTS

We confirmed that RPE is characterized by recruitment of polymorphonuclear leukocytes (PMNs), the release of PMN granular contents into the air spaces, and increased vascular permeability. These findings were highly correlated with increased interleukin-8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) concentrations in the BALF. Growth related oncogene (GRO) was detected in the BALF from only 2 of the 7 reexpanded lungs while TNFalpha was not detected in any rabbits. A similar but less severe inflammatory response to the reexpanded lung was found in the contralateral lung.

CONCLUSIONS

IL-8 and MCP-1 may play important roles in the development of RPE; the inflammatory response is independent of TNFalpha and unilateral reexpansion of the lung induces an inflammatory response not only in the reexpanded lung but also in the contralateral lung.

Amniotic fluid lipopolysaccharide-binding protein and soluble CD14 as mediators of the inflammatory response in preterm labor

OBJECTIVE

Our purpose was to determine the association of lipopolysaccharide-binding protein (LBP) and soluble CD14 (sCD14) with the proinflammatory response among women in preterm labor. The binding of lipopolysaccharide (LPS) with LBP and sCD14 activates macrophages at LPS concentrations up to 1000 times lower than required with LPS alone. LBP and sCD14 in amniotic fluid could explain the high concentrations of cytokines present in the amniotic fluid of culture-positive women and the presence of cytokines in the amniotic fluid of culture-negative women.

STUDY DESIGN

A cohort of 169 afebrile women in preterm labor with intact membranes had amniotic fluid collected by transabdominal amniocentesis for culture and for LBP, sCD14, and interleukin 6 (IL-6) determinations by enzyme-linked immunosorbent assay. IL-6 levels of >2 ng/mL were considered elevated. Statistical analyses included analysis of variance, multiple comparisons with Bonferroni correction, and linear regression.

RESULTS

All 169 amniotic fluid samples had measurable LBP and sCD14. Subjects were categorized by amniotic fluid culture results and IL-6 concentration into 3 groups: (1) positive amniotic fluid culture, (2) negative amniotic fluid culture, elevated IL-6 concentration, and (3) negative amniotic fluid culture, low IL-6 level. Geometric mean LBP and sCD14 levels differed significantly among groups such that levels were approximately twice as high among pregnancies with positive amniotic fluid culture or elevated IL-6 compared with those without evidence of inflammation (both P <.001). sCD14 was inversely associated with enrollment gestational age independent of amniotic fluid culture results and IL-6 concentrations. Among culture negative, low IL-6 pregnancies, sCD14 decreased 3.5% for each additional week of gestation (95% confidence interval [CI], 0.01%-6.4%; P =.02). LBP levels showed a similar trend in this group (P =.09). One hundred eleven subjects had detectable IL-6 levels. Among these subjects, IL-6 increased by 2.1-fold for every 10-fold increase in LBP (95% CI, 1.1-4.0; P =.02) and by 28.4-fold for every 10-fold increase in sCD14 (95% CI, 10.4-77.4; P <.001) with adjustment for gestational age by linear regression.

CONCLUSIONS

LBP and sCD14 are present in amniotic fluid of preterm pregnancies and are linearly associated with amniotic fluid IL-6 concentrations. These molecules may amplify the cytokine response and thereby help explain the presence of cytokines in amniotic fluid when culturable quantities of microbes are absent.

Anti-interleukin 8 autoantibody: interleukin 8 complexes in the acute respiratory distress syndrome. Relationship between the complexes and clinical disease activity

Increased levels of interleukin 8 (IL-8) are found in bronchoalveolar lavage (BAL) fluids from patients with the acute respiratory distress syndrome (ARDS). However, IL-8 is not an efficient predictor of the course of ARDS. Our prior studies demonstrated that IL-8 present in lung fluids from patients with ARDS is associated with anti-IL-8 autoantibodies (anti-IL-8:IL-8 complexes). These data led us to hypothesize that the complexes might better predict the development of acute lung injury. Accordingly, we measured concentrations of free and complexed IL-8 in BAL fluids from 19 patients at risk and 45 with established ARDS on Days 1, 3, 7, 14, and 21 after the onset of ARDS. The concentrations of anti-IL-8:IL-8 complexes in patients with ARDS on Day 1 were significantly higher than in patients at risk (p < 0.05). There was a significant association between anti-IL-8:IL-8 complex concentrations and the onset of ARDS (p = 0.03). Similarly, anti-IL-8:IL-8 complex concentrations were significantly higher in patients on Day 1 of ARDS who later died (p < 0.05), and the association between high anti-IL-8: IL-8 complex concentrations and the probability of dying was significant (p = 0.03). The presence of anti-IL-8:IL-8 complexes in BAL fluids of patients with ARDS is an important prognostic indicator for the development and outcome of ARDS.

Nitric oxide and nitrotyrosine in the lungs of patients with acute respiratory distress syndrome

Nitric oxide (NO) end-products (nitrate and nitrite) are present in bronchoalveolar lavage (BAL) fluid of patients with inflammatory lung diseases. Reactive oxygen-nitrogen intermediates damage macromolecules by oxidation or nitration of critical residues in proteins. The goal of this study was to measure NO end-products (nitrate+ nitrite), in BAL fluid before and after the onset of acute respiratory distress syndrome (ARDS) and to determine if these products are associated with expression of inducible nitric oxide synthase enzyme (iNOS) in BAL cells and nitration of BAL proteins. We performed bronchoalveolar lavage (BAL) in patients at risk for ARDS (n = 19), or with ARDS (n = 41) on Days 1, 3, 7, 14, and 21 after onset, and measured total nitrite (after reducing nitrate to nitrite) and protein-associated nitrotyrosine concentration in each BAL fluid sample. Cytospin preparations of BAL cells were analyzed by immunocytochemistry for iNOS and nitrotyrosine. Nitrate+nitrite were detected in BAL fluid from patients at risk for ARDS, and for as long as 21 d after the onset of ARDS. Nitrotyrosine was detectable in all BAL fluid samples for as long as 14 d after the onset of ARDS (range, 38.8 to 278.5 pmol/mg of protein), but not in BAL of normal volunteers. Alveolar macrophages of patients with ARDS were positive for iNOS and nitrotyrosine, and remained positive for as long as 14 d after onset of ARDS. The BAL nitrate+nitrite did not predict the onset of ARDS, but the concentration was significantly higher on Days 3 and 7 of ARDS in patients who died. Thus, NO end products accumulate in the lungs before and after onset of ARDS; iNOS is expressed at high levels in AM during ARDS; and nitration of intracellular and extracellular proteins occurs in the lungs in ARDS. The data support the concept that NO-dependent pathways are important in the lungs of patients before and after the onset of ARDS.

Septic shock and acute lung injury in rabbits with peritonitis: failure of the neutrophil response to localized infection

The major goal of this study was to investigate the mechanisms that link the host response to a local infection in the peritoneal cavity with the development of sepsis and lung injury. Rabbits were infected by intraperitoneal inoculation of fibrin clots containing Escherichia coli at 10(8), 10(9), or 10(10) cfu/clot. Physiologic, bacteriologic, and inflammatory responses were monitored, and the lungs were examined postmortem. At a dose of 10(8) cfu/clot the animals had resolving infection, and a dose of 10(9) cfu/clot resulted in persistent infection at 24 h, with minimal systemic manifestations. In contrast, inoculation of 10(10) cfu/clot resulted in rapidly lethal local infection, with septic shock and lung injury. The onset of septic shock was associated with a paradoxical lack of identifiable polymorphonuclear leukocytes (PMN; neutrophils) in the peritoneal cavity. The absence of PMN in the peritoneum was due in part to lysis of intraperitoneal PMN, because the peritoneal fluids contained free myeloperoxidase and induced rapid death of normal rabbit PMN in vitro. Although most animals became bacteremic, only those with a severe systemic inflammation response developed lung injury. These data show that control of an infection in the first compartment in which bacteria enter the host is a critical determinant of the systemic response. Above a threshold dose of bacteria, failure of the local neutrophil response is a key mechanism associated with deleterious systemic responses. Bacteremia alone is not sufficient to cause lung injury. Lung injury occurs only in the setting of a severe systemic inflammatory response and an inadequate leukocyte response at the primary site of infection.

Fas (CD95) induces alveolar epithelial cell apoptosis in vivo: implications for acute pulmonary inflammation

Activation of the Fas/FasL system induces apoptosis of susceptible cells, but may also lead to nuclear factor kappaB activation. Our goal was to determine whether local Fas activation produces acute lung injury by inducing alveolar epithelial cell apoptosis and by generating local inflammatory responses. Normal mice (C57BL/6) and mice deficient in Fas (lpr) were treated by intranasal instillation of the Fas-activating monoclonal antibody (mAb) Jo2 or an irrelevant control mAb, and studied 6 or 24 hours later using bronchoalveolar lavage (BAL), histopathology, DNA nick-end-labeling assays, and electron microscopy. Normal mice treated with mAb Jo2 had significant increases in BAL protein at 6 hours, and BAL neutrophils at 24 hours, as compared to lpr mice and to mice treated with the irrelevant mAb. Neutrophil recruitment was preceded by increased mRNA expression for tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-2, macrophage chemotactic protein-1, and interleukin-6, but not interferon-gamma, transforming growth factor-ss, RANTES, eotaxin, or IP-10. Lung sections from Jo2-treated normal mice showed neutrophilic infiltrates, alveolar septal thickening, hemorrhage, and terminal dUTP nick-end-labeling-positive cells in the alveolar septae and airspaces. Type II pneumocyte apoptosis was confirmed by electron microscopy. Fas activation in vivo results in acute alveolar epithelial injury and lung inflammation, and may be important in the pathogenesis of acute lung injury.

Inhibition of the tissue factor-thrombin pathway limits infarct size after myocardial ischemia-reperfusion injury by reducing inflammation

Functional inhibition of tissue factor (TF) has been shown to improve coronary blood flow after myocardial ischemia/reperfusion (I/R) injury. TF initiates the coagulation protease cascade, resulting in the generation of the serine protease thrombin and fibrin deposition. Thrombin can also contribute to an inflammatory response by activating various cell types, including vascular endothelial cells. We used a rabbit coronary ligation model to investigate the role of TF in acute myocardial I/R injury. At-risk areas of myocardium showed increased TF expression in the sarcolemma of cardiomyocytes, which was associated with a low level of extravascular fibrin deposition. Functional inhibition of TF activity with an anti-rabbit TF monoclonal antibody administered either 15 minutes before or 30 minutes after coronary ligation reduced infarct size by 61% (P = 0.004) and 44% (P = 0.014), respectively. Similarly, we found that inhibition of thrombin with hirudin reduced infarct size by 59% (P = 0.014). In contrast, defibrinogenating the rabbits with ancrod had no effect on infarct size, suggesting that fibrin deposition does not significantly contribute to infarct size. Functional inhibition of thrombin reduced chemokine expression and inhibition of either TF or thrombin reduced leukocyte infiltration. We propose that cardiomyocyte TF initiates extravascular thrombin generation, which enhances inflammation and injury during myocardial I/R.

Hyporesponsiveness of donor cells to lipopolysaccharide stimulation reduces the severity of experimental idiopathic pneumonia syndrome: potential role for a gut-lung axis of inflammation

Idiopathic pneumonia syndrome (IPS) is a major complication of allogeneic bone marrow transplantation (BMT). We have shown that experimental IPS is associated with increased levels of LPS and TNF-alpha in the bronchoalveolar lavage (BAL) fluid. We hypothesized that the deleterious effects of these inflammatory mediators in the lung may be linked to gut injury that develops after BMT. To test this hypothesis, we used mouse strains that differ in their sensitivity to LPS as donors in an experimental BMT model. Lethally irradiated C3FeB6F(1) hosts received BMT from either LPS-sensitive or LPS-resistant donors. Five weeks after BMT, LPS-resistant BMT recipients had significantly less lung injury compared with recipients of LPS-sensitive BMT. This effect was associated with reductions in TNF-alpha secretion (both in vitro and in vivo), BAL fluid LPS levels, and intestinal injury. The relationship between TNF-alpha, gut toxicity, and lung injury was examined further by direct cytokine blockade in vivo; systemic neutralization of TNF-alpha resulted in a significant reduction in gut histopathology, BAL fluid LPS levels, and pulmonary dysfunction compared with control-treated animals. We conclude that donor resistance to endotoxin reduces IPS in this model by decreasing the translocation of LPS across the intestinal border and systemic and pulmonary TNF-alpha production. These data demonstrate a potential etiologic link between gut and lung damage after BMT and suggest that methods that reduce inflammatory responses to LPS, and specifically, those that protect the integrity of the gut mucosa, may be effective in reducing IPS after BMT.

CD40L, but not CD40, is required for allergen-induced bronchial hyperresponsiveness in mice

Asthma is characterized by immunoglobulin (Ig) E production, infiltration of the respiratory mucosa by eosinophils (EOSs) and mononuclear cells, and bronchial hyperresponsiveness (BHR). Interaction of CD40 on B cells and antigen presenting cells, with its ligand (CD40L) expressed transiently on activated T cells, is known to augment both T cell-driven inflammation and humoral immune responses, especially IgE production. Considering both the prominent role of inflammation in asthma and the association of the disease with IgE, we hypothesized that CD40-CD40L interactions would be important in pathogenesis. To test this hypothesis, we subjected wild-type (WT) mice and animals lacking either CD40 or CD40L to repeated inhalation of Aspergillus fumigatus (Af ) antigen. Af-treated WT mice displayed elevated IgE levels, bronchoalveolar lavage and pulmonary tissue eosinophilic inflammation, and BHR. IgE production was markedly suppressed in both the CD40 -/- and CD40L -/- strains. However, pulmonary inflammation did not appear to be inhibited by either of these mutations. Paradoxically, development of BHR was prevented by the lack of CD40L but not by the absence of CD40. We conclude that CD40/CD40L interactions, although critical in the induction of IgE responses to inhaled allergen, are not required for the induction of EOS-predominant inflammation. CD40L, but not CD40, is necessary for the development of allergen-induced BHR.

Rabbit models of pneumonia, peritoneal sepsis, and lung injury

To study the mechanisms that link sepsis with ARDS, many animal models have been developed. In this chapter, a rabbit model of sepsis secondary to an intrapulmonary or intraabdominal infection has been described. One advantage of the rabbit model of sepsis is that this species produces the C-X-C chemokine, IL-8. In contrast, rodents, which are often used in studies of sepsis and ARDS, lack this important chemokine. A second advantage is the rabbit's size. This species is large enough so that the measurement of physiological parameters (e.g., mean arterial pressure, heart rate, etc.) is not difficult, but they are not so large that they require large quantities of precious reagents (e.g., recombinant proteins and MAbs). A disadvantage of the rabbit model is that there are fewer reagents (e.g., recombinant cytokines and MAbs) available for the study of inflammation in rabbits when compared to mice.

Tumor necrosis factor-alpha neutralization reduces lung injury after experimental allogeneic bone marrow transplantation

BACKGROUND

Idiopathic pneumonia syndrome (IPS) is a frequent and potentially fatal complication of bone marrow transplantation (BMT). We have previously shown that experimental IPS is associated with increased levels of lipopolysaccaride (LPS) and tumor necrosis factor-alpha (TNFalpha) in the bronchoalveolar lavage (BAL) fluid, and that administration of LPS to animals with extensive graft versus host exacerbated underlying lung injury (Blood 1996; 88: 3230).

METHODS

Lethally irradiated CBA mice received BMT from allogeneic (B10.BR) or syngeneic (CBA) donors. The role of TNFalpha in the exacerbation of pulmonary toxicity caused by LPS injection and in the evolution of IPS after allogeneic BMT was examined by neutralizing TNFalpha after BMT using a soluble binding protein (rhTNFR:Fc).

RESULTS

Five weeks after BMT, administration of rhTNFR:Fc dramatically reduced mortality and prevented the exacerbation of lung injury caused by LPS administration. This protective effect was associated with preservation of pulmonary function and with marked reductions of cells, neutrophils, and LPS in the BAL fluid of treated animals. TNFalpha neutralization from week 4 to 6 after allogeneic BMT effectively halted the progression of systemic GVHD and significantly reduced, but did not prevent lung injury that developed during the treatment period.

CONCLUSIONS

We conclude that TNFalpha is central to early LPS induced toxicity in this model and is a significant, but not the exclusive contributor to the development of IPS after allogeneic BMT.

Cholesterol decreases secretion of the secreted form of amyloid precursor protein by interfering with glycosylation in the protein secretory pathway

Cerebral deposits of beta-amyloid (betaA) are a major feature in Alzheimer's disease. betaA is derived from amyloid precursor protein (APP). APP is subject to N- and O-glycosylation and undergoes a series of proteolytic cleavages that lead to the release of betaA or of a non-amyloidogenic secreted form of APP (APPs). We used primary neuronal and glial cultures to investigate how cholesterol affects the production and secretion of APPs. Exposure to cholesterol for 2 h did not change the neuronal release of APPs; after 6 h APPs release was slightly lower, whereas 24 h of exposure decreased APPs in the medium by approx. 60%. The time courses were similar in astrocytes and microglia preparations. To verify whether the effect of cholesterol was a consequence of membrane rigidification we tested the activity of ganglioside GM1 and prion protein fragment PrP 106-126, which affect membrane fluidity similarly to cholesterol, on APPs secretion. Neither altered the production of APPs. APP mRNA and the total amount of APP in the cells were slightly decreased by cholesterol after 2 and 24 h respectively. Immunoblot analysis of APP associated with neuronal cells and astrocytes indicated that cholesterol progressively decreased the glycosylated forms of the protein; a similar tendency was noted in cells treated with brefeldin A and monensin, two substances that interfere with protein glycosylation. The cell-surface biotinylation method showed that in cholesterol-treated cells APP reached the plasma membrane. Our results indicate that cholesterol decreases the secretion of APPs by interfering with APP maturation and inhibiting glycosylation of the protein; although APP is inserted in the membrane it is not cleaved by alpha-secretase.

Effect of CD14 blockade in rabbits with Escherichia coli pneumonia and sepsis

CD14, a pattern recognition receptor found on myeloid cells, is a critical component of the innate immune system that mediates local and systemic host responses to Gram-negative and Gram-positive bacterial products. Previous studies in normal animals have tested the effect of CD14 blockade on the systemic response to i.v. LPS. The goals of the study were to determine whether CD14 blockade protected against the deleterious systemic response associated with Escherichia coli pneumonia and to determine whether this strategy affected the pulmonary response to tissue infection. Rabbits were pretreated with either anti-CD14 mAb or isotype control mAb at 2.5 mg/kg. E. coli (1 x 109 CFU) was inoculated into the lungs, and the animals were observed for either 4 or 24 h. The blockade of CD14 improved the mean arterial blood pressure (p = 0.001) and decreased the i.v. fluid requirements (p = 0.01). Although this therapy protected the vascular compartment, rabbits treated with anti-CD14 mAb had increased bacterial burdens in the bronchoalveolar lavage fluid recovered from the instilled lung (p = 0.005) and widened alveolar-arterial oxygen difference. Blockade of CD14 prevents the deleterious systemic responses that occur in sepsis; however, other measures are necessary to control bacterial proliferation at the primary site of infection.

Modulation of neutrophil apoptosis by granulocyte colony-stimulating factor and granulocyte/macrophage colony-stimulating factor during the course of acute respiratory distress syndrome

OBJECTIVE

To determine whether bronchoalveolar lavage fluid (BALF) from patients either at risk for the acute respiratory distress syndrome (ARDS) or with sustained ARDS modulates neutrophil apoptosis; to measure the BALF concentrations of the apoptosis inhibitors granulocyte colony-stimulating factor (G-CSF) and granulocyte/macrophage colony-stimulating factor (GM-CSF) before and after the onset of ARDS; and to determine whether the BALF concentrations of G-CSF and/or GM-CSF are associated with clinical outcome.

DESIGN

Prospective cohort study.

SETTING

Tertiary university hospital.

PATIENTS

Twenty patients at risk for ARDS and 45 patients with established ARDS.

INTERVENTIONS

Patients at risk for ARDS underwent bronchoalveolar lavage within 24 hrs of being identified, then again 72 hrs later. Patients with ARDS underwent bronchoalveolar lavage within 24 hrs of meeting ARDS criteria, then again on days 3, 7, and 14 of the disease.

MEASUREMENTS AND MAIN RESULTS

Normal peripheral blood neutrophil were incubated overnight in BALF from normal volunteers, from patients at risk for ARDS, or from patients with ARDS. neutrophil apoptosis was determined by flow cytometric analysis of annexin V binding. G-CSF and GM-CSF were measured in BALF by immunoassays. Compared with normal BALF, BALF from patients on days 1 and 3 of ARDS inhibited neutrophil apoptosis, but BALF from patients at later stages of ARDS, or from patients at risk for ARDS, did not. The BALF concentrations of both G-CSF and GM-CSF were elevated early in ARDS and decreased toward later stages. Patients who lived had significantly higher concentrations of GM-CSF in the BALF than those who died.

CONCLUSIONS

We conclude that the antiapoptotic effect of ARDS BALF on normal neutrophil is highest during early ARDS, and decreases during late ARDS. G-CSF and GM-CSF are present in BALF from patients with ARDS, and their concentrations parallel the antiapoptotic effect of ARDS BALF. These data support the concept that the life-span of neutrophil in the air spaces is modulated during acute inflammation. GM-CSF in the air spaces is associated with improved survival in patients with ARDS.

Serial changes in surfactant-associated proteins in lung and serum before and after onset of ARDS

The goal of this study was to determine the changes that occur in surfactant-associated proteins in bronchoalveolar lavage fluid (BAL) and serum of patients at risk for ARDS and during the course of ARDS. We found that the concentrations of SP-A and SP-B were low in the BAL of patients at risk for ARDS before the onset of clinically defined lung injury, whereas the concentration of SP-D was normal. In patients with established ARDS, BAL SP-A and SP-B concentrations were low during the entire 14-d observation period, but the median SP-D concentrations remained in the normal range. Immunoreactive SP-A and SP-D were not increased in the serum of patients at risk for ARDS, but both increased after the onset of ARDS to a maximum on Day 3 and remained elevated for as long as 14 d. The BAL SP-A concentrations were significantly lower in at-risk patients who developed ARDS, and no patient with a BAL SP-A concentration greater than 1.2 microg/ml developed ARDS. On Days 1 and 3 of ARDS, the BAL SP-D concentration was significantly lower in patients who died, and the BAL SP-D concentration was significantly related to the PI(O(2))/FI(O(2)) ratio. Thus, surfactant protein abnormalities occur before and after the onset of ARDS, and the responses of SP-A, SP-B, and SP-D differ in important ways. The BAL SP-A and SP-D measurements can be used to classify patients as high or low risk for progression to ARDS and/or death after the onset of ARDS. Strategies to increase these surfactant proteins in the lungs of patients with ARDS could be useful to modify the onset or the course of ARDS.

Genetic variability in pulmonary physiological, cellular, and antibody responses to antigen in mice

Wide differences among inbred mouse strains in susceptibility to develop components of asthmalike pulmonary changes would provide insights into the nature of the relationships among those components and set the stage for genetic approaches to their etiology. We therefore examined pulmonary pathophysiological and serum immunoglobulin (Ig)E responses in mice of 12 inbred strains sensitized intraperitoneally with ovalbumin (OVA) and repeatedly exposed to aerosolized OVA. One day after the last OVA exposure the intravenous methacholine (MCh) dose required to reduce lung conductance by 50% (ED(50)GL) in OVA-sensitized and exposed mice was reduced by 0 to 2.7-fold, compared with sham-sensitized mice, depending on the strain. In OVA-sensitized mice, bronchoalveolar lavage (BAL) eosinophils comprised from 3.3 +/- 3.1 (SD) to 91.2 +/- 5.0% of BAL cells and eosinophilic pulmonary inflammation varied from being nondetectable to widespread and severe. OVA-specific IgE concentrations ranged from less than 3 ng/ml to 455 ng/ml in different strains. Shifts in responsiveness correlated significantly with pulmonary eosinophilia among strains (r > 0.70, p < 0.001) but not with antigen-specific IgE levels (r = 0.55, p = 0.056). These results demonstrate that allergen- induced enhancement of cholinergic responsiveness, pulmonary eosinophil influx, and elevations of serum antigen-specific IgE levels are each genetically determined and are not always associated.

Pathogenesis of septic shock in Pseudomonas aeruginosa pneumonia

The pathogenesis of septic shock occurring after Pseudomonas aeruginosa pneumonia was studied in a rabbit model. The airspace instillation of the cytotoxic P. aeruginosa strain PA103 into the rabbit caused a consistent alveolar epithelial injury, progressive bacteremia, and septic shock. The lung instillation of a noncytotoxic, isogenic mutant strain (PA103DeltaUT), which is defective for production of type III secreted toxins, did not cause either systemic inflammatory response or septic shock, despite a potent inflammatory response in the lung. The intravenous injection of PA103 did not cause shock or an increase in TNF-alpha, despite the fact that the animals were bacteremic. The systemic administration of either anti-TNF-alpha serum or recombinant human IL-10 improved both septic shock and bacteremia in the animals that were instilled with PA103. Radiolabeled TNF-alpha instilled in the lung significantly leaked into the circulation only in the presence of alveolar epithelial injury. We conclude that injury to the alveolar epithelium allows the release of proinflammatory mediators into the circulation that are primarily responsible for septic shock. Our results demonstrate the importance of compartmentalization of inflammatory mediators in the lung, and the crucial role of bacterial cytotoxins in causing alveolar epithelial damage in the pathogenesis of acute septic shock in P. aeruginosa pneumonia.

Idiopathic pneumonia after bone marrow transplantation: cytokine activation and lipopolysaccharide amplification in the bronchoalveolar compartment

OBJECTIVE

To determine whether idiopathic pneumonia syndrome (IPS), a form of noninfectious lung injury that follows bone marrow transplantation, is associated with cytokine activation and increased susceptibility to lipopolysaccharide (LPS).

DESIGN

Case series.

SETTING

Tertiary referral center for marrow transplantation.

PATIENTS

Recipients with biopsy-confirmed IPS; normal volunteers and marrow transplant recipients without IPS were analyzed as controls.

MEASUREMENTS AND MAIN RESULTS

Levels of lymphocyte and macrophage-derived cytokines as well as components of the LPS, LPS-binding protein (LBP), and CD14 system in bronchoalveolar lavage (BAL) fluid were determined. We found evidence of increased vascular permeability (BAL protein) and inflammatory cytokine activation (interleukin-1, interleukin-2, interleukin-6, and tumor necrosis factor-alpha) in patients with IPS. Patients without IPS had BAL fluid cytokine and protein levels that were similar to levels in BAL fluid from normal volunteers. Moreover, components of the LPS amplification system (LBP and soluble CD14) were increased in patients with IPS but not in patients without IPS.

CONCLUSIONS

These results provide direct evidence for proinflammatory cytokine activation in IPS and suggest that these patients might be at increased risk for LPS-mediated injury through the LBP amplification pathway.

Soluble Fas ligand induces epithelial cell apoptosis in humans with acute lung injury (ARDS)

The goals of this study were to determine whether the Fas-dependent apoptosis pathway is active in the lungs of patients with the acute respiratory distress syndrome (ARDS), and whether this pathway can contribute to lung epithelial injury. We found that soluble Fas ligand (sFasL) is present in bronchoalveolar lavage (BAL) fluid of patients before and after the onset of ARDS. The BAL concentration of sFasL at the onset of ARDS was significantly higher in patients who died. BAL from patients with ARDS induced apoptosis of distal lung epithelial cells, which express Fas, and this effect was inhibited by blocking the Fas/FasL system using three different strategies: anti-FasL mAb, anti-Fas mAb, and a Fas-Ig fusion protein. In contrast, BAL from patients at risk for ARDS had no effect on distal lung epithelial cell apoptosis. These data indicate that sFasL is released in the airspaces of patients with acute lung injury and suggest that activation of the Fas/FasL system contributes to the severe epithelial damage that occurs in ARDS. These data provide the first evidence that FasL can be released as a biologically active, death-inducing mediator capable of inducing apoptosis of cells of the distal pulmonary epithelium during acute lung injury.

SLP-76 deficiency impairs signaling via the high-affinity IgE receptor in mast cells

SLP-76 is an adapter protein expressed in T cells and myeloid cells that is a substrate for ZAP-70 and Syk. SLP-76-deficient mice exhibit a profound block in T-cell development. We found that although SLP-76 is expressed in mouse mast cells, SLP-76(-/-) mice have normal numbers of mast cells in their skin and bronchi. SLP-76(-/-) mice are resistant to IgE-mediated passive anaphylaxis. SLP-76(-/-) mice sensitized with IgE anti-dinitrophenyl (DNP) and then challenged with DNP-HSA developed only mild and transient tachycardia, failed to increase their plasma histamine level, and all survived the antigen challenge. Bone marrow-derived mast cells (BMMCs) from SLP76(-/-) mice failed to release beta-hexosaminidase and to secrete IL-6 after FcepsilonRI cross-linking. Tyrosine phosphorylation of phospholipase C-gamma1 (but not of Syk) and calcium mobilization in response to IgE cross-linking were reduced in SLP-76-deficient BMMCs. These results suggest that SLP-76 plays an important role in FcepsilonRI-mediated signaling in mast cells.

Role of the type 1 TNF receptor in lung inflammation after inhalation of endotoxin or Pseudomonas aeruginosa

To determine the roles of the type 1 tumor necrosis factor (TNF) receptor (TNFR1) in lung inflammation and antibacterial defense, we exposed transgenic mice lacking TNFR1 [TNFR1(-/-)] and wild-type control mice to aerosolized lipopolysaccharide or Pseudomonas aeruginosa. After LPS, bronchoalveolar lavage fluid (BALF) from TNFR1(-/-) mice contained fewer neutrophils and less macrophage inflammatory protein-2 than BALF from control mice. TNF-alpha, interleukin-1beta, and total protein levels in BALF as well as tissue intercellular adhesion molecule-1 expression did not differ between the two groups. In contrast, lung inflammation and bacterial clearance after infection were augmented in TNFR1(-/-) mice. BALF from infected TNFR1(-/-) mice contained more neutrophils and TNF-alpha and less interleukin-1beta and macrophage inflammatory protein-2 than that from control mice, but protein levels were similarly elevated in both groups. Lung inflammation and bacterial clearance were also augmented in mice lacking both TNF receptors. Thus TNFR1 facilitates neutrophil recruitment after inhalation of lipopolysaccharide, in part by augmenting chemokine induction. In contrast, TNFR1 attenuates lung inflammation in response to live bacteria but does not contribute to increased lung permeability and is not required for the elimination of P. aeruginosa.

Expression and function of the chemokine receptors CXCR1 and CXCR2 in sepsis

Neutrophils (polymorphonuclear neutrophils; PMN) and a redundant system of chemotactic cytokines (chemokines) have been implicated in the pathogenesis of the acute respiratory distress syndrome in patients with sepsis. PMN express two cell surface receptors for the CXC chemokines, CXCR1 and CXCR2. We investigated the expression and function of these receptors in patients with severe sepsis. Compared with normal donors, CXCR2 surface expression was down-regulated by 50% on PMN from septic patients (p < 0.005), while CXCR1 expression persisted. In vitro migratory responses to the CXCR1 ligand, IL-8, were similar in PMN from septic patients and normal donors. By contrast, the migratory response to the CXCR2 ligands, epithelial cell-derived neutrophil activator (ENA-78) and the growth-related oncogene proteins, was markedly suppressed in PMN from septic patients (p < 0.05). Ab specific for CXCR1 blocked in vitro migration of PMN from septic patients to IL-8 (p < 0.05), but not to FMLP. Thus, functionally significant down-regulation of CXCR2 occurs on PMN in septic patients. We conclude that in a complex milieu of multiple CXC chemokines, CXCR1 functions as the single dominant CXC chemokine receptor in patients with sepsis. These observations offer a potential strategy for attenuating adverse inflammation in sepsis while preserving host defenses mediated by bacteria-derived peptides such as FMLP.

Mast cell activation is not required for induction of airway hyperresponsiveness by ozone in mice

Exposure to ambient ozone (O3) is associated with increased exacerbations of asthma. We sought to determine whether mast cell degranulation is induced by in vivo exposure to O3 in mice and whether mast cells play an essential role in the development of pulmonary pathophysiological alterations induced by O3. For this we exposed mast cell-deficient WBB6F1-kitW/kitW-v (kitW/kitW-v) mice and the congenic normal WBB6F1 (+/+) mice to air or to 1 or 3 parts/million O3 for 4 h and studied them at different intervals from 4 to 72 h later. We found evidence of O3-induced cutaneous, as well as bronchial, mast cell degranulation. Polymorphonuclear cell influx into the pulmonary parenchyma was observed after exposure to 1 part/milllion O3 only in mice that possessed mast cells. Airway hyperresponsiveness to intravenous methacholine measured in vivo under pentobarbital anesthesia was observed in both kitW/kitW-v and +/+ mice after exposure to O3. Thus, although mast cells are activated in vivo by O3 and participate in O3-induced polymorphonuclear cell infiltration into the pulmonary parenchyma, they do not participate detectably in the development of O3-induced airway hyperresponsiveness in mice.

Ischemia-reperfusion lung injury in rabbits: mechanisms of injury and protection

To study the mechanisms responsible for ischemia-reperfusion lung injury, we developed an anesthetized rabbit model in which the effects of lung deflation, lung inflation, alveolar gas composition, hypothermia, and neutrophils on reperfusion pulmonary edema could be studied. Rabbits were anesthetized and ventilated, and the left pulmonary hilum was clamped for either 2 or 4 h. Next, the left lung was reperfused and ventilated with 100% oxygen. As indexes of lung injury, we measured arterial oxygenation, extravascular lung water, and the influx of a vascular protein (131I-labeled albumin) into the extravascular space of the lungs. The principal results were that 1) all rabbits with the deflation of the lung during ischemia for 4 h died of fulminant pulmonary edema within 1 h of reperfusion; 2) inflation of the ischemic lung with either 100% oxygen, air, or 100% nitrogen prevented the reperfusion lung injury; 3) hypothermia at 6-8 degreesC also prevented the reperfusion lung injury; 4) although circulating neutrophils declined during reperfusion lung injury, there was no increase in interleukin-8 levels in the plasma or the pulmonary edema fluid, and, furthermore, neutrophil depletion did not prevent the reperfusion injury; and 5) ultrastructural studies demonstrated injury to both the lung endothelium and the alveolar epithelium after reperfusion in deflated lungs, whereas the inflated lungs had no detectable injury. In summary, ischemia-reperfusion injury to the rabbit lung can be prevented by either hypothermia or lung inflation with either air, oxygen, or nitrogen.

The role of leukocyte emigration and IL-8 on the development of lipopolysaccharide-induced lung injury in rabbits

Leukocyte emigration and alveolar macrophage-derived cytokines may contribute to lung microvascular injury associated with adult respiratory distress syndrome. We have used mAbs against cell adhesion molecules on leukocytes (anti-CD18 and anti-CD49d) or against IL-8 to investigate these contributions. Intratracheal (i.t.) instillation of LPS (50 microg/kg) caused a significant increase in bronchoalveolar lavage polymorphonuclear leukocytes (PMNs) without an increase in mononuclear cells (MNCs) or an increase in lung permeability. Injection of LPS (10 microg/kg) i.v. at 24 h after i.t. LPS caused significant increases in bronchoalveolar lavage PMNs, MNCs, IL-8, and monocyte chemotactic protein-1, as well as increases in lung permeability. Rabbits that were administered i.t. LPS followed by i.v. LPS and treated with anti-CD18 mAb had a significantly lower lung permeability index and emigration of fewer PMNs but no change in MNC emigration compared with saline treatment. Anti-IL-8 mAb treatment resulted in a significantly lower lung permeability index with no change in PMN emigration compared with no treatment. These results suggest that PMN emigration is necessary but not sufficient for the development of LPS-induced lung injury, and that IL-8 plays a significant role in PMN-dependent lung injury, independent of PMN emigration.

Host reactive donor T cells are associated with lung injury after experimental allogeneic bone marrow transplantation

Noninfectious lung injury is common after allogeneic bone marrow transplantation (BMT), but its association with acute graft-versus-host disease (GVHD) is unclear. Using a murine BMT system where donor and host differ by multiple minor histocompatibility (H) antigens, we investigated the nature of lung injury and its relationship both to systemic GVHD and host-reactive donor T cells. Lethally irradiated CBA hosts received syngeneic BMT or allogeneic (B10.BR) T-cell-depleted (TCD) bone marrow (BM) with and without the addition of T cells. Six weeks after BMT, significant pulmonary histopathology was observed in animals receiving allogeneic BMT compared with syngeneic controls. Lung damage was greater in mice that received allogeneic T cells and developed GVHD, but it was also detectable after TCD BMT when signs of clinical and histologic acute GVHD were absent. In each setting, lung injury was associated with significant alterations in pulmonary function. Mature, donor (Vbeta6(+) and Vbeta3(+)) T cells were significantly increased in the broncho-alveolar lavage (BAL) fluid of all allogeneic BMT recipients compared with syngeneic controls, and these cells proliferated and produced interferon-gamma (IFN-gamma) to host antigens in vitro. These in vitro responses correlated with increased IFN-gamma and tumor necrosis factor-alpha (TNF-alpha) in the BAL fluid. We conclude that alloreactive donor lymphocytes are associated with lung injury in this allogeneic BMT model. The expansion of these cells in the BAL fluid and their ability to respond to host antigens even when systemic tolerance has been established (ie, the absence of clinical GVHD) suggest that the lung may serve as a sanctuary site for these host reactive donor T cells. These findings may have important implications with regard to the evaluation and treatment of pulmonary dysfunction after allogeneic BMT even when clinical GVHD is absent.

Elevated transforming growth factor-alpha levels in bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) frequently results in a fibroproliferative response that precludes effective alveolar repair. Transforming growth factor-alpha (TGF-alpha), a potent epithelial and mesenchymal cell mitogen, may modulate the response to lung injury. In this study, we determined whether bronchoalveolar lavage fluid (BALF) concentrations of TGF-alpha are increased during the first 2 wk after the onset of ARDS and, if so, whether increased TGF-alpha levels in lavage fluid are associated with increased levels of procollagen peptide III (PCP III), a biological marker of fibroproliferation, and with increased fatality rates. We enrolled 74 consecutive patients with ARDS prospectively identified on admission to the intensive care unit of a tertiary care hospital, and 11 patients with chronic interstitial lung disease. Thirteen healthy volunteers served as control subjects. TGF-alpha concentrations were measured in BALF recovered on Days 3, 7, and 14 after the onset of ARDS (total of 130 lavage samples). TGF-alpha was detected in the lavage fluid of 90% of patients with ARDS (67 of 74), and in 100% of patients with idiopathic pulmonary fibrosis (IPF) (10 of 10), but in none of 13 normal volunteers. At each day tested, the median lavage TGF-alpha level of patients with ARDS was significantly higher than that of normals. The overall fatality rate was 45% (33 of 74 patients). In a univariate analysis, the median TGF-alpha levels in nonsurvivors were 1.5-fold higher at Day 7 (p = 0.06) and 1.8-fold higher at Day 14 (p = 0.048). The fatality rate was 4 times higher (CI 1.6, 17.5) for patients with both increased lavage TGF-alpha and PCP III concentrations at Day 7 than for patients with low TGF-alpha and PCP III values, indicating a synergistic relationship between TGF-alpha and PCP III. We conclude that increased levels of TGF-alpha in BALF are common in patients with ARDS and that lavage TGF-alpha is associated with a marker of the fibroproliferative response in sustained ARDS.

Clinical application of the Mycobacterium tuberculosis direct test: case report, literature review, and proposed clinical algorithm

The relatively new Mycobacterium tuberculosis direct test (MTDT) enzymatically amplifies M tuberculosis complex 16s ribosomal RNA. The sensitivity of the test ranges from 75 to 100%, with specificity of 95 to 100%, positive predictive value between 78% and 100%, and negative predictive value between 95% and 100%. Similar test characteristics have been documented in nonrespiratory specimens and in specimens that ultimately grow nontuberculous mycobacterium (NTM). This test allows for rapid identification of M tuberculosis in the smear-positive patient and may greatly improve sensitivity over acid-fast bacilli smear alone. A negative test result with a positive smear suggests infection with NTM or Mycobacterium avium complex. We present a case that illustrates the value of MTDT for analysis of tissue specimens in immunocompromised patients with suspected mycobacterial disease and review the rapidly developing literature about this test. We propose an algorithm using MTDT, acid-fast smear, and mycobacterial culture for the diagnosis and treatment of the immunocompromised patient with suspected mycobacterial infection.

Quantitative comparison of C-X-C chemokines produced by endotoxin-stimulated human alveolar macrophages

The C-X-C chemokines are a structurally related and functionally redundant family of proteins with neutrophil chemotactic activity. Many of the C-X-C chemokines are produced by endotoxin-stimulated alveolar macrophages (AMs), but knowledge of their relative quantities and their relative contributions to the total chemotactic activity released from these cells is incomplete. Human AMs were stimulated with or without Escherichia coli endotoxin for 2, 4, 8, and 24 h. The mRNA sequences of interleukin (IL)-8, the 78-amino acid epithelial cell-derived neutrophil activator (ENA-78), growth-related protein (GRO) alpha, GRObeta, and GROgamma were cloned by PCR and identified by sequence analysis. The relative mRNA quantities were compared by Northern analysis, and IL-8 was found to predominate. Similarly, IL-8 protein concentrations in the cell supernatants were consistently higher than either the ENA-78 or GRO concentration, and by 24 h, IL-8 concentrations were 10-fold higher than those of the other C-X-C chemokines. Blocking polyclonal antibodies to IL-8 substantially reduced the chemotactic activity in the AM supernatants, whereas antibodies to ENA-78 and GRO had little or no effect. We conclude that IL-8 is the predominant C-X-C chemokine and the dominant neutrophil chemoattractant accumulating in 24-h supernatants of lipopolysaccharide-stimulated human AMs. These studies provide insight into potentially effective strategies of interrupting AM-derived inflammatory signals in the lungs.

Epicutaneous sensitization with protein antigen induces localized allergic dermatitis and hyperresponsiveness to methacholine after single exposure to aerosolized antigen in mice

Our understanding of the pathogenesis of atopic dermatitis (AD) and its relationship to asthma remains incomplete. Herein, we describe a murine model of epicutaneous (EC) sensitization to the protein allergen, chicken egg albumin, ovalbumin (OVA), which results in a rise in total and OVA-specific serum IgE and leads to the development of a dermatitis characterized by infiltration of CD3(+) T cells, eosinophils, and neutrophils and by local expression of mRNA for the cytokines IL-4, IL-5, and interferon-gamma. A single exposure of the EC sensitized mice to aerosolized OVA induced eosinophilia in the bronchoalveolar lavage fluid and airway hyperresponsiveness to intravenous methacholine as assessed by measurement of pulmonary dynamic compliance (Cdyn). These results suggest a possible role for EC exposure to antigen in atopic dermatitis and in the development of allergic asthma.

Rapid fluorescence-based measurement of neutrophil migration in vitro

We have standardized a new chemotaxis chamber that uses fluorescence as the cellular marker for the measurement of leukocyte migration in vitro in disposable 96-well microplates. This new fluorescence-based assay is a robust assay because filter pore size, cell density, filter composition, and filter thickness do not affect PMN migration towards interleukin-8 or the complement fragment, C5a. When compared to two separate chemotaxis assays in which the migrated cells are counted visually, the fluorescence-based assay was more rapid, less labor intensive, and more sensitive. This new assay is a significant advance in the measurement of leukocyte migration in vitro.

Neutrophil apoptosis in the acute respiratory distress syndrome

Little is known about neutrophil (PMN) apoptosis in the acute respiratory distress syndrome (ARDS). We uses morphologic criteria to count apoptotic PMN in bronchoalveolar lavage fluid (BAL) of 35 patients on Days 1, 3, 7, 14, and 21 of ARDS and 13 patients on Days 1 and 3 of risk for ARDS. We found that the proportion of apoptotic PMN in BAL was low throughout the course of ARDS. There was no significant difference between the percentage of apoptotic PMN in patients at risk and patients with established ARDS or between patients who lived (2.4%) and patients who died (1.8%). When normal human PMN were incubated in ARDS BAL, a significantly lower proportion became apoptotic (50 +/- 4%), as compared with PMN incubated in lavage fluid from normal volunteers (76 +/- 7%, p < 0.05). This antiapoptotic effect of ARDS BAL was blocked by immunodepleting BAL of G-CSF and GM-CSF. We conclude that the proportion of apoptotic PMN recovered from the lungs of patients with ARDS is low throughout the course of ARD S. Furthermore, BAL from patients with ARDS prolongs survival of normal human PMN in vitro, and this effect is partially mediated by G-CSF and GM-CSF.

Lipopolysaccharide binding protein and soluble CD14 receptor protein in amniotic fluid and cord blood in patients at term

OBJECTIVES

Our purpose was to examine whether lipopolysaccharide binding protein and soluble CD14 are present in amniotic fluid and to determine whether the lipopolysaccharide binding protein and soluble CD14 concentrations are associated with indicators of infection or labor at term. A lipopolysaccharide-lipopolysaccharide binding protein complex activates macrophages through soluble CD14 at lipopolysaccharide concentrations up to 100 times lower than required with lipopolysaccharide alone. Thus lipopolysaccharide binding protein and soluble CD14 in amniotic fluid could explain the high concentrations of cytokines found in amniotic fluid of culture-positive patients and may even explain the presence of cytokines in some culture-negative patients.

STUDY DESIGN

Healthy women at term undergoing cesarean section had amniotic fluid, chorioamnion, decidua, and cord blood obtained. Lipopolysaccharide binding protein was measured by enzyme-linked immunosorbent assay. Amniotic fluid was cultured and assayed for cytokines, and the chorioamnion and decidua were cultured and examined histologically.

RESULTS

Lipopolysaccharide binding protein and soluble CD14 were present in all amniotic fluids and fetal cord blood. An elevated level of lipopolysaccharide binding protein (270 ng/ml/mg of protein) was present in the amniotic fluid of 12 (36%) of the 33 patients. An elevated level was associated with microorganisms in the chorioamnion and decidua, cytokines (tumor necrosis factor-alpha, interleukin-6, and interleukin-8) in amniotic fluid, histologic chorioamnionitis, and labor. Among patients in labor, the concentration of lipopolysaccharide binding protein appeared independent of microorganisms in the amniotic fluid.

CONCLUSIONS

Lipopolysaccharide binding protein and soluble CD14 are present in amniotic fluid, and concentrations of lipopolysaccharide binding protein are elevated in patients in labor with and without evidence of infection. Lipopolysaccharide binding protein and soluble CD14 may mediate intrauterine inflammatory responses at term.

Increased phagocyte Fc gammaRI expression and improved Fc gamma-receptor-mediated phagocytosis after in vivo recombinant human interferon-gamma treatment of normal human subjects

Recombinant human interferon-gamma (rhIFN-gamma) decreases the frequency of serious infections in patients with chronic granulomatous disease (CGD) through an unknown mechanism. To test the hypothesis that it exerts a beneficial effect by enhancing clearance of microbes from the bloodstream and tissues, normal human subjects were treated in vivo with rhIFN-gamma. Phagocyte opsonic receptor expression, serum opsonin levels, and phagocytosis of bacteria were then measured. A 4.7-fold increase in neutrophil expression of the high-affinity Fc gamma-receptor (Fc gammaRI) was observed that peaked 48 hours after the initiation of rhIFN-gamma treatment (P < .05). Monocyte expression of Fc gammaRI, Fc gammaRII, Fc gammaRIII, CD11a, CD11b, CD18, and HLA-DR also significantly increased with peak expression at 48 hours. Phagocytosis by neutrophils of killed Staphylococcus aureus opsonized with heat-inactivated pooled human serum significantly improved after rhIFN-gamma treatment (P < .05) and correlated with Fc gammaRI expression by neutrophils (r = .8, P < .001). This increase in ingestion could be inhibited by anti-Fc gammaRI monoclonal antibodies. Levels of the serum opsonin lipopolysaccharide-binding protein also significantly increased after in vivo rhIFN-gamma (P < .05). These results suggest that the protective effect of rhIFN-gamma in patients with CGD may involve improved microbial clearance. Moreover, improved phagocyte trafficking may occur secondary to increased expression of monocyte beta2-integrins. Because these IFN-gamma-related improvements in host defense were seen in normal hosts, rhIFN-gamma may have broader applications in the treatment of various disorders of immunity in addition to its demonstrated efficacy in CGD.

Persistence of pulmonary pathology and abnormal lung function in IL-3/GM-CSF/IL-5 beta c receptor-deficient mice despite correction of alveolar proteinosis after BMT

Mice deficient for the IL-3/GM-CSF/IL-5 beta c receptor (beta cR KO) develop lung disease similar to that seen in human pulmonary alveolar proteinosis (PAP) which includes lymphocytic infiltration around airways and vessels and the progressive accumulation of surfactant and macrophages within the alveolar space. We investigated bone marrow transplantation (BMT) as a curative treatment of PAP in beta cR KO mice by semiquantitative histologic analysis and evaluation of pulmonary function. BMT from wild-type (WT) donors into lethally irradiated beta cR KO recipients (WT --> KO) led to the complete resolution of alveolar protein accumulation and to normalization of BAL fluid cellularity and macrophage morphology. However, detailed microscopic analysis of lung tissue revealed the persistence of significant cellular infiltrates in WT --> KO recipients which were equivalent to those seen in KO --> KO animals. Evaluation of pulmonary function demonstrated that only dynamic compliance (Cdyn) and not airway conductance (G[L]) was significantly improved in the WT --> KO group compared to KO --> KO animals and that both of these measurements remained significantly abnormal when compared to WT --> WT controls. We conclude, that although BMT for PAP reverses alveolar macrophage and protein accumulation, it does not decrease the interstitial inflammatory component of this disease. The importance of this residual pathology is demonstrated by the incomplete correction of alveolar function (Cdyn) and lack of improvement in increased airway resistance (G[L]). These findings may have important implications with regard to the extent that BMT can be considered a potential curative procedure for this clinical disorder.

A sensitive immunoassay to detect the alpha-chemokine GRO in rabbit blood and lung fluids

GRO-alpha, GRO-beta and GRO-gamma are closely related peptides that stimulate growth of tumor cells and activate leukocytes in acute inflammatory reactions. In order to study the biology of GRO peptides in the lungs of experimental animals, we have developed and characterized a sensitive and specific immunoassay for rabbit GRO, and used this assay to measure GRO in rabbit lung fluids and plasma. GRO was cloned from a rabbit cDNA library and expressed in Escherichia coli. Specific goat polyclonal antibodies were used to create an antigen-capture immunoassay. The assay is sensitive to approximately 30 pg/ml GRO and does not crossreact with rabbit IL-8 or MCP-1, or human GRO. The assay accurately measures GRO in rabbit bronchoalveolar lavage fluid, plasma and serum. Rabbit erythrocytes bind little GRO and do not interfere with the detection of GRO in lung fluids. Circulating GRO was detected in the plasma of 4 of 6 pathogen-free rabbits, but the function of circulating GRO in normal animals is uncertain. This immunoassay will facilitate the study of the biology of GRO in rabbits with acute and chronic inflammation in the lungs and other tissues.