Lung defense mechanisms (first of two parts)

Lung cell toxicological effects of 3D printer aerosolized filament byproducts

As 3D printing has become more compact and affordable, the use of the technology has become more prevalent across household, classroom, and small business settings. The emissions of fused filament fabrication (FFF) 3D printers consist of volatile organic compounds (VOCs) and aerosolized particulate matter (PM) dependent upon the filament in use. This study investigates the hazards posed by these emissions through aerosol characterization and cell exposure. Seventeen filaments were obtained from five manufacturers, consisting of fourteen plastic filaments (polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), or polycarbonate (PC) polymers) and three filaments with metal filler (copper, bronze, and steel). For 1-h trials, BEAS-2B human bronchial epithelial cells were directly exposed to aerosolized 3D printer emissions at the air-liquid interface (ALI). Particle characterization showed ABS filaments produced more PM and VOC emissions with particles in the ultrafine size range. ABS filaments also elicited a greater biological response, with significant shifts in mitochondrial activity compared to the PLA filaments. Significant changes in amounts of glutathione (GSH) were observed after ABS and PLA emission exposure. Exposure to emissions from the steel filament resulted in the lowest average amount of glutathione, though insignificant, and a significantly lower mitochondrial activity, revealing a unique cause for concern among filaments tested. 3D printer emissions and subsequent cell responses appear filament-dependent, and users should mitigate personal exposure to aerosols.

Lung Deposition and Inspiratory Flow Rate in Patients with Chronic Obstructive Pulmonary Disease Using Different Inhalation Devices: A Systematic Literature Review and Expert Opinion

BACKGROUND

Our aim was to describe: 1) lung deposition and inspiratory flow rate; 2) main characteristics of inhaler devices in chronic obstructive pulmonary disease (COPD).

METHODS

A systematic literature review (SLR) was conducted to analyze the features and results of inhaler devices in COPD patients. These devices included pressurized metered-dose inhalers (pMDIs), dry powder inhalers (DPIs), and a soft mist inhaler (SMI). Inclusion and exclusion criteria were established, as well as search strategies (Medline, Embase, and the Cochrane Library up to April 2019). In vitro and in vivo studies were included. Two reviewers selected articles, collected and analyzed data independently. Narrative searches complemented the SLR. We discussed the results of the reviews in a nominal group meeting and agreed on various general principles and recommendations.

RESULTS

The SLR included 71 articles, some were of low-moderate quality, and there was great variability regarding populations and outcomes. Lung deposition rates varied across devices: 8%-53% for pMDIs, 7%-69% for DPIs, and 39%-67% for the SMI. The aerosol exit velocity was high with pMDIs (more than 3 m/s), while it is much slower (0.84-0.72 m/s) with the SMI. In general, pMDIs produce large-sized particles (1.22-8 μm), DPIs produce medium-sized particles (1.8-4.8 µm), and 60% of the particles reach an aerodynamic diameter <5 μm with the SMI. All inhalation devices reach central and peripheral lung regions, but the SMI distribution pattern might be better compared with pMDIs. DPIs' intrinsic resistance is higher than that of pMDIs and SMI, which are relatively similar and low. Depending on the DPI, the minimum flow inspiratory rate required was 30 L/min. pMDIs and SMI did not require a high inspiratory flow rate.

CONCLUSION

Lung deposition and inspiratory flow rate are key factors when selecting an inhalation device in COPD patients.

Increasing the Quantity of Lungs for Transplantation Using High-Frequency Chest Wall Oscillation: A Proposal

The use of chest physiotherapy in donor patient management occupies an established place in most lung procurement protocols. Although its merits remain controversial and uncorroborated by direct data, some studies support the efficacy of chest physiotherapy in a variety of pulmonary patient populations. Comparative studies have shown that an airway clearance technology utilizing high-frequency chest wall oscillation clears pulmonary secretions as well as or better than chest physiotherapy, but has few of its contraindications and disadvantages. The implementation of high-frequency chest wall oscillation as part of the donor lung procurement protocol may increase rates of successful lung recovery by providing effective clearance of obstructing pulmonary secretions containing destructive by-products of inflammation and entrapped pathogens. High-frequency chest wall oscillation may also improve arterial blood gas values, a critical factor in increasing lung procurement rates. Although speculative, the benefits of high-frequency chest wall oscillation on donor lungs might improve perfusion and oxygenation of other organs for possible transplantation.

Mesothelioma from asbestos exposures: Epidemiologic patterns and impact in the United States

Mesothelioma, a rare tumor, is highly correlated with asbestos exposure. Mesothelioma, similar to all asbestos-related diseases, is dose/intensity dependent to some degree, and studies showed the risk of mesothelioma rises with cumulative exposures. Multiple processes occur in an individual before mesothelioma occurs. The impact of mesothelioma in the United States has been continuous over the last half century, claiming between 2,000 and 3,000 lives each year. Mesothelioma is a preventable tumor that is more frequently reported as associated with asbestos exposure among men than women. However, the rate of asbestos-associated mesothelioma is on the rise among women due to better investigation into their histories of asbestos exposure. It is of interest that investigators detected asbestos-associated cases of mesothelioma in women from nonoccupational sources-that is, bystander, incidental, or take-home exposures. It is postulated that asbestos-associated mesotheliomas, in both men and women, are likely underreported. However, with the implementation of the most recent ICD-10 coding system, the correlation of mesothelioma with asbestos exposure is expected to rise to approximately 80% in the United States. This study examined the demographic and etiological nature of asbestos-related mesothelioma.

Deposition of inhaled particles in the lungs

Inhaled medication is the first-line treatment of diseases such as asthma or chronic obstructive pulmonary disease. Its effectiveness is related to the amount of drug deposited beyond the oropharyngeal region, the place where the deposit occurs and its distribution (uniform or not). It is also important to consider the size of the inhaled particles, the breathing conditions, the geometry of the airways and the mucociliary clearance mechanisms. Currently, mathematical models are being applied to describe the deposition of inhaled drugs based on the size of the particles, the inspiratory flow and the anatomical distribution of the bronchial tree. The deposition of particles in the small airways gets maximum attention from pharmaceutical companies and is of great interest as it is related with a better control in patients receiving these drugs.

Fungal Infections

The incidence of invasive fungal infections has increased dramatically over the past two decades, mostly due to an increase in the number of immunocompromised patients.1–4 Patients who undergo chemotherapy for a variety of diseases, patients with organ transplants, and patients with the acquired immune deficiency syndrome have contributed most to the increase in fungal infections.5 The actual incidence of invasive fungal infections in transplant patients ranges from 15% to 25% in bone marrow transplant recipients to 5% to 42% in solid organ transplant recipients.6,7 The most frequently encountered are Aspergillus species, followed by Cryptococcus and Candida species. Fungal infections are also associated with a higher mortality than either bacterial or viral infections in these patient populations. This is because of the limited number of available therapies, dose-limiting toxicities of the antifungal drugs, fewer symptoms due to lack of inflammatory response, and the lack of sensitive tests to aid in the diagnosis of invasive fungal infections.1 A study of patients with fungal infections admitted to a university-affiliated hospital indicated that community-acquired infections are becoming a serious problem; 67% of the 140 patients had community-acquired fungal pneumonia.8

Accelerated mortality from hydrocephalus and pneumonia in mice with a combined deficiency of SPAG6 and SPAG16L reveals a functional interrelationship between the two central apparatus proteins

SPAG6 and SPAG16L are proteins localized to the "9+2" axoneme central apparatus. Both are essential for sperm motility and male fertility. These two proteins are also expressed in other tissues containing ciliated cells, such as brain and lung. To study the effects of combined deficiency of these two proteins, a double mutant mouse model was created. The double mutant mice displayed a more profound phenotype of growth retardation and hydrocephalus compared to mice nullizygous for SPAG6 and SPAG16L alone. The double mutant mice died younger, and mortality was significantly higher than in single mutant mice. In addition, the double mutant mice demonstrated pneumonia and its complications, including hemorrhage, edema, and atelectasis, phenotypes not observed in mice nullizygous for mutations in the individual genes. No other cilia-related phenotypic change was detected in double mutant mice including lateralization defects. The ultrastructure of cilia in both the brain and lung of the double mutant mice appeared normal. This model of combined SPAG6 and SPAG16L deficiency provides a new platform to study primary ciliary dyskinesia. The findings also demonstrate that SPAG6 and SPAG16L have related roles in controlling the function of cilia in the brain and lung.

Parasympathetic control of airway submucosal glands: central reflexes and the airway intrinsic nervous system

Airway submucosal glands produce the mucus that lines the upper airways to protect them against insults. This review summarizes evidence for two forms of gland secretion, and hypothesizes that each is mediated by different but partially overlapping neural pathways. Airway innate defense comprises low level gland secretion, mucociliary clearance and surveillance by airway-resident phagocytes to keep the airways sterile in spite of nearly continuous inhalation of low levels of pathogens. Gland secretion serving innate defense is hypothesized to be under the control of intrinsic (peripheral) airway neurons and local reflexes, and these may depend disproportionately on non-cholinergic mechanisms, with most secretion being produced by VIP and tachykinins. In the genetic disease cystic fibrosis, airway glands no longer secrete in response to VIP alone and fail to show the synergy between VIP, tachykinins and ACh that is observed in normal glands. The consequent crippling of the submucosal gland contribution to innate defense may be one reason that cystic fibrosis airways are infected by mucus-resident bacteria and fungi that are routinely cleared from normal airways. By contrast, the acute (emergency) airway defense reflex is centrally mediated by vagal pathways, is primarily cholinergic, and stimulates copious volumes of gland mucus in response to acute, intense challenges to the airways, such as those produced by very vigorous exercise or aspiration of foreign material. In cystic fibrosis, the acute airway defense reflex can still stimulate the glands to secrete large amounts of mucus, although its properties are altered. Importantly, treatments that recruit components of the acute reflex, such as inhalation of hypertonic saline, are beneficial in treating cystic fibrosis airway disease. The situation for recipients of lung transplants is the reverse; transplanted airways retain the airway intrinsic nervous system but lose centrally mediated reflexes. The consequences of this for gland secretion and airway defense are poorly understood, but it is possible that interventions to modify submucosal gland secretion in transplanted lungs might have therapeutic consequences.

Kinetics of influenza A virus infection in humans

Currently, little is known about the viral kinetics of influenza A during infection within an individual. We utilize a series of mathematical models of increasing complexity, which incorporate target cell limitation and the innate interferon response, to examine influenza A virus kinetics in the upper respiratory tracts of experimentally infected adults. The models were fit to data from an experimental H1N1 influenza A/Hong Kong/123/77 infection and suggest that it is important to include the eclipse phase of the viral life cycle in viral dynamic models. Doing so, we estimate that after a delay of approximately 6 h, infected cells begin producing influenza virus and continue to do so for approximately 5 h. The average lifetime of infected cells is approximately 11 h, and the half-life of free infectious virus is approximately 3 h. We calculated the basic reproductive number, R(0), which indicated that a single infected cell could produce approximately 22 new productive infections. This suggests that antiviral treatments have a large hurdle to overcome in moderating symptoms and limiting infectiousness and that treatment has to be initiated as early as possible. For about 50% of patients, the curve of viral titer versus time has two peaks. This bimodal behavior can be explained by incorporating the antiviral effects of interferon into the model. Our model also compared well to an additional data set on viral titer after experimental infection and treatment with the neuraminidase inhibitor zanamivir, which suggests that such models may prove useful in estimating the efficacies of different antiviral therapies for influenza A infection.

Increasing the quantity of lungs for transplantation using high-frequency chest wall oscillation: a proposal

The use of chest physiotherapy in donor patient management occupies an established place in most lung procurement protocols. Although its merits remain controversial and uncorroborated by direct data, some studies support the efficacy of chest physiotherapy in a variety of pulmonary patient populations. Comparative studies have shown that an airway clearance technology utilizing high-frequency chest wall oscillation clears pulmonary secretions as well as or better than chest physiotherapy, but has few of its contraindications and disadvantages. The implementation of high-frequency chest wall oscillation as part of the donor lung procurement protocol may increase rates of successful lung recovery by providing effective clearance of obstructing pulmonary secretions containing destructive by-products of inflammation and entrapped pathogens. High-frequency chest wall oscillation may also improve arterial blood gas values, a critical factor in increasing lung procurement rates. Although speculative, the benefits of high-frequency chest wall oscillation on donor lungs might improve perfusion and oxygenation of other organs for possible transplantation.

Aspiration of activated charcoal elicits an increase in lung microvascular permeability

BACKGROUND

Gastric decontamination with orally administered activated charcoal is the recommended treatment for many poisonings. However, ingestion of central nervous system depressants resulting in loss of protective airway reflexes may result in pulmonary aspiration of activated charcoal. Although activated charcoal has been reported to be an inert substance, evidence suggests that pulmonary aspiration of charcoal is associated with lung edema formation and pulmonary compromise. This study tested the hypothesis that intratracheal instillation of activated charcoal disrupts the integrity of the lung microvascular barrier.

METHODS

The capillary filtration coefficient (Kf,c), a sensitive measure of lung microvascular permeability, was determined isogravimetrically prior to and after intratracheal instillation of activated charcoal 0.04 g/kg (12% weight/vol solution, pH 7.4) or an equal volume of sterile water in isolated, perfused rat lungs. Arterial blood gas analysis was determined prior to and after tracheal instillation of activated charcoal or sterile water in a separate group of animals.

RESULTS

Intratracheal instillation of activated charcoal resulted in a significant increase in pulmonary microvascular permeability compared to lungs treated with sterile water or control lungs (delta Kf,c = +0.21 +/- 0.076; -0.014 +/- 0.04; and -0.041 +/- 0.02 mL/min/cm H2O/100 g lung tissue, respectively, p < 0.05 ANOVA). There was no significant difference in baseline blood gases in the 3 experimental groups. There was a significant decrease in arterial Po2, bicarbonate, and pH in animals administered activated charcoal compared to time-matched controls and animals administered sterile water.

CONCLUSIONS

Intratracheal instillation of activated charcoal is associated with a significant increase in lung microvascular permeability and arterial blood gas derangements. The effects of activated charcoal on pulmonary microvascular barrier integrity may contribute to the lung edema formation and pulmonary compromise observed following clinical aspiration of activated charcoal.

Airway infection

Bronchitis in its acute and chronic forms with recurrent acute exacerbations is one of the most common reasons for physician visits, accounting for a significant cost to the health-care system, lost work days, and increased morbidity and mortality. Smoking and recurrent lower respiratory tract infections are major risk factors for chronic bronchitis. Therefore, smoking cessation and vaccination strategies are cornerstones of management in terms of halting disease progression and reducing the frequency of infectious exacerbations. Bacterial infection is the main culprit in acute flares of the disease. Routine antimicrobial therapy fails in a significant number of patients, and therapeutic failures lead to increased costs. Several stratification schemes have been proposed to improve initial antimicrobial selection. These schemes identify patient's age, severity of underlying pulmonary dysfunction, frequency of exacerbations, and the presence of comorbid illnesses as predictors for likely pathogens and to guide antimicrobial selection. This approach may reduce the risk for treatment failure, which would have significant medical and economic implications. Improved understanding of the roles of airway inflammation and infection in the pathogenesis of progressive airway disease, in addition to future studies examining the efficacy of newer classes of antimicrobials, should guide physicians to target early and effective treatment to high-risk patients.

Bronchopulmonary disease in the cat: historical, physical, radiographic, clinicopathologic, and pulmonary functional evaluation of 24 affected and 15 healthy cats

The results of clinical and pulmonary functional evaluation of 24 cats with bronchopulmonary disease and 15 healthy cats are presented. Affected cats had historical evidence of excessive reflexes (coughing, sneezing); physical evidence of airway secretions (crackles), obstruction (wheezing), and increased tracheal sensitivity; radiographic evidence of bronchial and interstitial lung disease; and cytological evidence of airway inflammation or mucous secretions. Bacterial isolates from healthy and affected cats were predominantly Gram-negative rods, indicating that bronchi of cats are not always sterile and that normal flora should be considered in interpreting cultures from cats with suspected bronchopulmonary disease. Cats were grouped according to relative disease severity based on scored historical, physical, and radiographic abnormalities. The mean (+/- standard deviation) baseline lung resistance measurement in healthy cats was 28.9 cm H2O/L/s (+/- 6.2 cm H2O/L/s), whereas in mildly, moderately, and severely affected cats it was 38.3 cm H2O/L/s (+/- 21.5 cm H2O/L/s), 44.8 cmH2O/L/s (+/- 7.7 cm H2O/L/s), and 105.2 cm H2O/L/s (+/- 66.9 cm H2O/L/s), respectively. In healthy cats, dynamic lung compliance was 19.8 (+/- 7.4), whereas in mildly, moderately, and severely affected cats it was 14.7 mL/cm H2O (+/- 3.8 mL/cm H2O), 17.7 mL/cm H2O (+/- 6.9 mL/cm H2O), and 13.0 mL/cm H2O (+/- 7.9 mL/cm H2O), respectively. Thus, airway obstruction was present in many of the affected cats. Based on acute response to the bronchodilator, terbutaline, airway obstruction was partially reversible in many affected cats, although the degree of reversibility varied. Furthermore, based on bronchoprovocation testing, 6 (of 7) affected cats evaluated also had increased airway responsiveness to aerosolized methacholine.

Raising airway resistance in laryngectomees increases tissue oxygen saturation

The physiological airflow resistance from the anterior nares to the upper trachea has recently been documented. This resistance is thought to be important in preventing alveolar collapse and in maintaining the optimum lung ventilation: perfusion ratio. This resistance is lost in laryngectomees who may have a subsequent decline in lung function and arterial oxygen saturation. A stoma filter with a resistance approximating to that of the normal upper airway has been developed and laryngectomees who wear this device demonstrate a rapid increase in tissue oxygen saturation (median increase: 1.4 kPa, P = 0.0087) without significantly altering tissue carbon dioxide saturation. This finding will have a major impact on the future rehabilitation of laryngectomees and those with a temporary tracheostomy.

Granulocyte-macrophage colony-stimulating factor overrides the immunosuppressive function of corticosteroids on rat pulmonary dendritic cells

Pulmonary dendritic cells (DC) are present in extremely small numbers, but they are the most potent antigen-presenting cells in the lungs. Pure populations of DC can be isolated from the lung following collagen digestion, Percoll gradient centrifugation, removal of phagocytic cells and flow cytometric sorting for cells which exhibit high levels of surface major histocompatibility complex (MHC) class II molecules. Exogenous GM-CSF enhances this immunostimulatory capacity of the pulmonary DC. Soluble factors produced by type II airway epithelial cells and interstitial macrophages also enhance the immunostimulating capacity of pulmonary DC while alveolar macrophages suppress it. Thus, the function of DC may be regulated by locally produced cytokines. Corticosteroids are widely used as immunosuppressive agents in pharmacotherapy. While these agents are known to inhibit T cell proliferation and macrophage activation, their effects on DC are not known. We found that dexamethasone (Dex) pretreatment resulted in about a 50% reduction in the immunostimulatory capacity of rat pulmonary DC. This was associated with downregulation of MHC class II (Ia) expression. Dex-induced suppression of DC function could be restored with GM-CSF. We conclude that corticosteroids downregulate antigen-presenting capacity by direct suppression of pulmonary DC. This immunosuppressive effect of corticosteroids on DC may, however, be abrogated by exogenous GM-CSF. Corticosteroids and GM-CSF are therapeutic agents with potent direct immunomodulating effects on DC.

Effects of posture and accumulated airway secretions on tracheal mucociliary transport in the horse

Tracheal mucociliary clearance was determined in horses by measuring the rostrad transport of the radiopharmaceutical 99mtechnetium-sulphur colloid following deposition on the tracheal epithelium by intratracheal injection. The effects of head position (head elevated to normal standing position vs head lowered) and of accumulated purulent secretions on tracheal mucociliary clearance were evaluated for the first time in the horse. In normal horses tracheal mucociliary clearance was greatly accelerated by lowering the head so that the cranial trachea was lower than the caudal trachea. Horses confined with their heads elevated for 24 hours developed an accumulation of purulent airway secretions (and associated increased numbers of bacteria) in the lower respiratory tract and showed a decrease in tracheal mucociliary clearance when compared with their previously measured rate when the lower airway contained only normal secretions. These findings have implications for management practices where horses are prevented from lowering their heads, such as transportation and cross-tying, which may therefore contribute to lower respiratory tract disease in horses.

Resistance, humidity and temperature of the tracheal airway

Patients after laryngectomy are subject to a high incidence of chest complaints. In attempting to reduce these a number of 'new nose' stoma filters have recently been introduced which claim to humidify and warm air, filter particulate matter and, by increasing tracheal airway resistance, to improve lung function. Our study defines the normal tracheal temperature, humidity and resistance values which were obtained from 16 patients with a normal upper respiratory tract. These parameters will allow the available filters to be evaluated objectively and may lead to the development of a more physiological 'new nose'.

The regulation of pulmonary immunity

No evidence has emerged which suggests that the principles of immunity derived from studies on cells from other body sites are contradicted in the lung and its associated lymphoid tissue. What is clear, however, is that the environment dictates the types of cells, their relationship to one another, and what perturbing events will set in motion either the development of an "active" immune response or tolerance. Investigating mechanisms for the development of lung immunity has increased our understanding of how human diseases develop and is continuing to suggest new ways to manipulate pulmonary immune responses. Demonstration that lung cells regulate both nonspecific inflammation and immunity through the expression of adhesion molecules and the secretion of cytokines offers hope for ways to design more effective vaccines, enhance microbial clearance in immunosuppressed hosts, and to suppress manifestations of immunologically mediated lung disease. Important lung diseases targeted for intensive research efforts in the immediate future are tuberculosis, asthma, and fibrotic lung disease. Perhaps even the common cold might be conquered. Considering the pace of current research on lung immunity, it may not be too ambitious to predict that these diseases may be conquered in the next decade.

Host defenses against respiratory infection

The respiratory tract is protected from infection by its formidable mechanical and cellular defenses, supplemented when necessary by inflammatory and immune responses. Impairments in these defenses develop as a result of underlying disease and therapeutic interventions. Specific defects in host defenses often predispose to infection with particular etiologic agents. New opportunities for the therapeutic augmentation of defenses are emerging that may be particularly helpful in the care of immunocompromised patients.

Physiological changes due to age. Implications for respiratory drug therapy

The pulmonary system is modified in various ways over time and it is particularly vulnerable to environmental insults. Of particular interest are the implications of aging for therapy of respiratory illnesses. The changes in pulmonary structure and function due simply to aging, and changes due to diseases, should be distinguished from each other. The great reserve function of the lung permits reasonable physical capacity in healthy individuals despite aging changes. In principle, loss of function equivalent to more than one lung is necessary to impair aerobic capacity at any age. Elderly people are subject to the same respiratory diseases as younger adults but may manifest them differently. They may present in atypical ways such as in bacterial pneumonia, tuberculosis, and asthma, all modified by anatomical alterations or deterioration of immunological defence mechanisms. Accumulation of toxic substances over time such as cigarette smoke or environmental pollutants may give rise to chronic bronchitis, emphysema, bronchogenic carcinoma and interstitial lung disease. Changes in the number or function of airway receptors modulate responses to bronchodilator drugs. Chronic inflammation of the bronchial wall has blurred the distinction between traditional asthma and chronic bronchitis and emphysema, and similar drug therapy can be useful for all. Adverse reactions to respiratory drugs such as theophylline, oral corticosteroids, and isoniazid increase with age. As more data accumulate, drug therapy of respiratory diseases in older patients will become more effective and safer.

Feline bronchopulmonary disease

This author is aware that not all cats fit so neatly into these subcategories. It is hoped, however, that through increased awareness of the differences between cats with bronchopulmonary disease, we can begin to focus and refine our diagnostic and therapeutic efforts and more accurately predict the prognosis of individual cats. The pulmonary functional changes in the cats presented here lend credence to the clinical use of these airway disease subtypes. However, relative to human disease syndromes, our current understanding of feline bronchopulmonary disease is in its infancy. One can only speculate as to why these cats developed airway inflammation in the first place. Constant exposure to dust through litter use or upper respiratory tract infections, seem to be likely causes. But, why do only certain cats become clinically ill when all cats are potentially exposed to similar conditions? Owing to the diversity of disease present in these cats, it is likely that multiple etiologies are involved. Alpha 1-antiprotease deficiency, for example, is a known genetic defect associated with the development of panacinar emphysema in homozygous humans. It is conceivable that similar genetic defects could be present in individual cats of the Siamese breed, as this breed is overrepresented in this syndrome and some of these cats appear to follow a progressive disease course.

A factor secreted by a human pulmonary alveolar epithelial-like cell line blocks T-cell proliferation between G1 and S phase

Because the pulmonary alveolar space is both the site of gas exchange for respiration and a portal of entry for foreign antigen, immunologic interactions within that space must be meticulously controlled. Alveolar epithelial cells are ideally situated to play a role in immune regulation within the alveolar space. We have used A549 cells, a cell line that is derived from a human alveolar cell carcinoma and that has been used as a model for alveolar type II epithelial cells, to examine the potential role of alveolar epithelial cells in local pulmonary immune regulation. Medium conditioned by confluent monolayers of A549 cells suppressed proliferation by human peripheral blood mononuclear cells (PBMC) stimulated with lectin, anti-CD3 antibodies, calcium ionophore and phorbol ester, or in a mixed leukocyte reaction. PBMC that had been incubated in and then removed from A549-conditioned medium went on to proliferate normally. Because the suppressive effect was abrogated by heating or acidification and was not blocked by neutralizing antibody to transforming growth factor-beta 1, this effect could not be attributed to transforming growth factor-beta. The factor mediating this effect has an approximate molecular weight of 70,000 D by gel filtration chromatography. Nonalveolar, pulmonary carcinoma cell lines did not exert this immunosuppressive influence nor did the alveolar epithelial cells inhibit proliferation by the transformed, Jurkat, T-cell line. Cell cycle analysis demonstrated that PBMC exposed to A549 cell-conditioned medium failed to enter S phase after mitogen stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in lymphocyte subpopulations in patients treated with cefodizime for acute lower respiratory tract infections

The influence of cefodizime (CDZ) on CD4 and CD8 lymphocytes was investigated in patients with lower respiratory tract infection and underlying respiratory diseases. Ten men and one woman were treated with CDZ 1 g i.m. b.i.d. for ten days. The infecting organisms were Haemophilus influenzae (5), Streptococcus pneumoniae (2) and Escherichia coli (1). No adverse events were reported. Nine patients were clinically cured; two required further antibiotic therapy. Leucocyte counts decreased significantly during treatment. Lymphocyte counts and CD4 cells both increased significantly in absolute and relative numbers, while there was a much smaller increase in CD8 cells. This resulted in a significant increase in the CD4/CD8 ratio. These effects of CDZ might be of benefit for immunocompromised patients with bacterial infections.

Alveolar epithelial cells block lymphocyte proliferation in vitro without inhibiting activation

In the face of constant exposure to inhaled antigens, precise local regulation of immune responses in the pulmonary alveolar space is essential to achieve a delicate balance between host defense and excessive immune responses that are incompatible with the primary physiologic function of the lung. We postulated that the cells of the alveolar epithelium may have an immunoregulatory role in the lung. Therefore, we have examined the effects of primary cultures of rat type II alveolar epithelial cells on lymphocyte proliferation and on the expression of a number of markers of T-cell activation. Monolayers of alveolar epithelial cells suppressed proliferation and DNA synthesis by concanavalin A-stimulated rat splenocytes. Suppression of [3H]thymidine incorporation was independent of the dose of mitogen and was also apparent when lymphocytes were stimulated with phorbol esters and calcium ionophore, suggesting that the effect was independent of cell surface binding of the lectin. Suppression was reversed 48 h after lectin-stimulated splenocytes were removed from co-culture with alveolar epithelial cells. Despite inhibition of lymphocyte proliferation, other markers of T-cell activation were induced normally in lymphocytes cultured with alveolar epithelial cells. Culture with alveolar epithelial cells did not inhibit the the production of interleukin-2 by stimulated lymphocytes. Furthermore, by fluorescence-activated cell sorter analysis, equal proportions of stimulated lymphocytes in culture alone or with alveolar epithelial cell monolayers were induced to express receptors for interleukin-2 and for transferrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of vitamin A-deficiency and inflammation on the conducting airway epithelium of Syrian golden hamsters

The effects of vitamin A-deficiency and inflammation were studied in the conducting airways of Syrian golden hamsters. An important goal of the study was to characterize epithelial changes that occur early in vitamin A-deficiency, that might precede yet predispose to infection, and precipitate inflammatory changes in the lungs. Age-matched vitamin A-replete control and vitamin A-deprived hamsters were killed at 33 days of age (preweight-plateau); at 41 days of age (weight plateau-early weight loss); and at 48-55 days of age (prolonged weight plateau followed by weight loss). A tablet containing bromodeoxyuridine (BrdU) was implanted subcutaneously into each hamster 7 h before it was killed. No changes were seen in the conducting airway epithelium of vitamin A-deprived hamsters in the preweight plateau. However, labelling of secretory cells for BrdU was reduced 6-7 fold in the epithelium lining the lobar bronchus (p less than 0.0002) and the bronchioles (p less than 0.0001), and the proportions of ciliated cells were decreased (p less than 0.0001) at both airway levels in vitamin A-deficient hamsters in the weight plateau-early weight loss stage. Changes in cellular morphology were minimal in the intrapulmonary airway epithelium at this time but a few small focal patches of epidermoid metaplasia were seen in the tracheal epithelium. Small foci of inflammation were closely associated with the airways in the weight plateau, and the inflammation became more widespread when the deficiency was prolonged. The results suggest that the defense of the lungs to infection was impaired initially in the vitamin A-deficient hamsters by a widespread reduction in the numbers of ciliated cells throughout the epithelium of the conducting airways (trachea, bronchi, bronchioles). At the foci of inflammation, labelling of epithelial secretory cells for BrdU was greatly increased at all airway levels. A highly stratified cornifying epidermoid metaplasia developed in the tracheal epithelium, and goblet cell metaplasia developed in the cranial portion of the lobar bronchus, in association with submucosal inflammation. Goblet cell metaplasia appeared to be the only abnormality that was not reversed when vitamin A was restored to the diet.

Pulmonary host defenses and oropharyngeal pathogens

The lower respiratory tract is repetitively inoculated with oropharyngeal bacteria and yet pneumonia is an infrequent event. Efficient mechanisms of antibacterial defense are present in the respiratory tract that eliminate microbes before their presence or multiplication leads to disease in the majority of instances. Resident pulmonary defenses consist of aerodynamic defenses, the mucociliary apparatus, alveolar macrophages, complement, and surfactant. These resident defenses can be augmented by the development of an inflammatory response or the development of specific immunity. Significant species variability exists in the efficiency and mechanisms of clearance for oropharyngeal organisms. Streptococci are cleared promptly, Branhamella catarrhalis is cleared slowly, whereas non-typable Haemophilus influenzae multiply before being cleared. A dual phagocytic system of alveolar macrophages and recruited polymorphonuclear leukocytes is required for clearance of most oropharyngeal microbes. Systemic immunization can significantly enhance clearance of non-typable H. influenzae, suggesting immunoprophylaxis might be possible for this organism.

Effect of primary immunization on pulmonary clearance of nontypable Haemophilus influenzae

Nontypable Haemophilus influenzae (NTHI) is being increasingly recognized as a cause of both adult pneumonia and acute infectious exacerbations in chronic bronchitis. We used a mouse model to study the immune enhancement of pulmonary clearance of NTHI after a primary immunization. BALB/c mice were immunized with whole NTHI either by intraperitoneal (i.p.) or intratracheal (i.t.) routes. There was 10-fold more NTHI-directed antibody detected in the serum of the i.p.-immunized mice than in the serum from the i.t.-immunized animals. Western blot analysis revealed that these antibodies were directed against both NTHI lipooligosaccharide and the various outer membrane proteins of NTHI. The development of NTHI-directed antibodies in serum was associated with significant enhancement of early pulmonary clearance of NTHI. Six hours after delivery of an endobronchial challenge with NTHI, the i.p.-immunized mice had cleared most of the organisms from their lungs, while the i.t.-immunized mice did not clear NTHI any more rapidly than did unimmunized mice. Serum from the i.p.-immunized mice caused more than 99% uptake of NTHI in an in vitro opsonophagocytic assay, while serum from i.t.-immunized mice stimulated little or no phagocytosis of this organism. Opsonophagocytosis of NTHI was obtained with bronchoalveolar lavage (BAL) fluid collected from i.p.-immunized mice 6 h after, but not before, an endobronchial challenge with NTHI. Intravenous injection of an opsonic IgG monoclonal antibody directed against NTHI lipooligosaccharide resulted in both the appearance of this antibody in the alveolar spaces of the unperturbed lung and enhanced pulmonary clearance of NTHI. These data indicate that the i.p. (systemic) route of immunization is more effective than the i.t. route in establishing pulmonary immunity to NTHI in this model system. Furthermore, immune enhancement of clearance of NTHI from the lungs after a primary immunization apparently results from the exudation of opsonic and bactericidal antibodies from the serum into the alveolae in response to the inflammatory challenge.

Perioperative risk assessment. Common misconceptions

Proper assessment of the preoperative patient is a blend of the art and science of medicine. The body of literature dealing with the various facets of this assessment has grown in the past few years. Unfortunately, this core of knowledge is neither well taught to residents-in-training nor well appreciated by many practicing physicians. Thus, evaluation of the surgical patient is often guided by personal anecdotes and unjustified assumptions. Seven common misconceptions are addressed in this article.

The effect of bacterial products on ciliary function

Mucociliary clearance protects the respiratory epithelium against inhaled particles. There is in vitro evidence that some bacteria produce factors that cause ciliary slowing, dyskinesia, and stasis. These changes may predominantly affect ciliary function alone or be associated with epithelial disruption and cell death. Some factors act immediately, while others can take up to a number of days to achieve effect. It is postulated that rapidly acting factors may be involved during bacterial colonization, allowing the bacterium time (by slowing clearance) to penetrate the mucociliary barrier and reach putative receptors on the epithelial surface. The compounds might similarly facilitate contiguous spread through the bronchial tree and augment the tissue damage caused by the host inflammatory response during chronic bronchial sepsis. Future work should define more clearly the in vivo significance of the largely in vitro observations made to date.