A study of plasma proteins in the sol phase of sputum from patients with chronic bronchitis

Well-controlled mucosal exudation of plasma proteins in airways with intact and regenerating epithelium

Superficial, systemic microcirculations, distinct from the pulmonary circulation, supply the mucosae of human nasal and conducting airways. Non-injurious, inflammatory challenges of the airway mucosa cause extravasation without overt mucosal oedema. Instead, likely reflecting minimal increases in basolateral hydrostatic pressure, circulating proteins/peptides of all sizes are transmitted paracellularly across the juxtaposed epithelial barrier. Thus, small volumes of extravasated, unfiltered bulk plasma appear on the mucosal surface at nasal and bronchial sites of challenge. Importantly, the plasma-exuding mucosa maintains barrier integrity against penetrability of inhaled molecules. Thus, one-way epithelial penetrability, strict localization, and well-controlled magnitude and duration are basic characteristics of the plasma exudation response in human intact airways. In vivo experiments in human-like airways demonstrate that local plasma exudation is also induced by non-sanguineous removal of epithelium over an intact basement membrane. This humoral response results in a protective, repair-promoting barrier kept together by a fibrin-fibronectin net. Plasma exudation stops once the provisional barrier is substituted by a new cellular cover consisting of speedily migrating repair cells, which may emanate from all types of epithelial cells bordering the denuded patch. Exuded plasma on the surface of human airways reflects physiological microvascular-epithelial cooperation in first line mucosal defense at sites of intact and regenerating epithelium.

Role of the humoral immune response during COVID-19: guilty or not guilty?

Systemic and mucosal humoral immune responses are crucial to fight respiratory viral infections in the current pandemic of COVID-19 caused by the SARS-CoV-2 virus. During SARS-CoV-2 infection, the dynamics of systemic and mucosal antibody infections are affected by patient characteristics, such as age, sex, disease severity, or prior immunity to other human coronaviruses. Patients suffering from severe disease develop higher levels of anti-SARS-CoV-2 antibodies in serum and mucosal tissues than those with mild disease, and these antibodies are detectable for up to a year after symptom onset. In hospitalized patients, the aberrant glycosylation of anti-SARS-CoV-2 antibodies enhances inflammation-associated antibody Fc-dependent effector functions, thereby contributing to COVID-19 pathophysiology. Current vaccines elicit robust humoral immune responses, principally in the blood. However, they are less effective against new viral variants, such as Delta and Omicron. This review provides an overview of current knowledge about the humoral immune response to SARS-CoV-2, with a particular focus on the protective and pathological role of humoral immunity in COVID-19 severity. We also discuss the humoral immune response elicited by COVID-19 vaccination and protection against emerging viral variants.

Human IgG and IgA responses to COVID-19 mRNA vaccines

SARS-CoV-2 spike antigen-specific IgG and IgA elicited by infection mediate viral neutralization and are likely an important component of natural immunity, however, limited information exists on vaccine induced responses. We measured COVID-19 mRNA vaccine induced IgG and IgA in serum serially, up to 145 days post vaccination in 4 subjects. Spike antigen-specific IgG levels rose exponentially and plateaued 21 days after the initial vaccine dose. After the second vaccine dose IgG levels increased further, reaching a maximum approximately 7-10 days later, and remained elevated (average of 58% peak levels) during the additional >100 day follow up period. COVID-19 mRNA vaccination elicited spike antigen-specific IgA with similar kinetics of induction and time to peak levels, but more rapid decline in serum levels following both the 1st and 2nd vaccine doses (<18% peak levels within 100 days of the 2nd shot). The data demonstrate COVID-19 mRNA vaccines effectively induce spike antigen specific IgG and IgA and highlight marked differences in their persistence in serum.

Early humoral defence: Contributing to confining COVID-19 to conducting airways?

Early airway responses to severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) infection are of interest since they could decide whether coronavirus disease‐19 (COVID‐19) will proceed to life‐threatening pulmonary disease stages. Here I discuss endothelial‐epithelial co‐operative in vivo responses producing first‐line, humoral innate defence opportunities in human airways. The pseudostratified epithelium of human nasal and tracheobronchial airways are prime sites of exposure and infection by SARS‐CoV‐2. Just beneath the epithelium runs a profuse systemic microcirculation. Its post‐capillary venules respond conspicuously to mucosal challenges with autacoids, allergens and microbes, and to mere loss of epithelium. By active venular endothelial gap formation, followed by transient yielding of epithelial junctions, non‐sieved plasma macromolecules move from the microcirculation to the mucosal surface. Hence, plasma‐derived protein cascade systems and antimicrobial peptides would have opportunity to operate jointly on an unperturbed mucosal lining. Similarly, a plasma‐derived, dynamic gel protects sites of epithelial sloughing‐regeneration. Precision for this indiscriminate humoral molecular response lies in restricted location and well‐regulated duration of plasma exudation. Importantly, the endothelial responsiveness of the airway microcirculation differs distinctly from the relatively non‐responsive, low‐pressure pulmonary microcirculation that non‐specifically, almost irreversibly, leaks plasma in life‐threatening COVID‐19. Observations in humans of infections with rhinovirus, coronavirus 229E, and influenza A and B support a general but individually variable early occurrence of plasma exudation in human infected nasal and tracheobronchial airways. Investigations are warranted to elucidate roles of host‐ and drug‐induced airway plasma exudation in restriction of viral infection and, specifically, whether it contributes to variable disease responses following exposure to SARS‐CoV‐2.

IgA dominates the early neutralizing antibody response to SARS-CoV-2

Humoral immune responses are typically characterized by primary IgM antibody responses followed by secondary antibody responses associated with immune memory and composed of IgG, IgA, and IgE. Here, we measured acute humoral responses to SARS-CoV-2, including the frequency of antibody-secreting cells and the presence of SARS-CoV-2-specific neutralizing antibodies in the serum, saliva, and bronchoalveolar fluid of 159 patients with COVID-19. Early SARS-CoV-2-specific humoral responses were dominated by IgA antibodies. Peripheral expansion of IgA plasmablasts with mucosal homing potential was detected shortly after the onset of symptoms and peaked during the third week of the disease. The virus-specific antibody responses included IgG, IgM, and IgA, but IgA contributed to virus neutralization to a greater extent compared with IgG. Specific IgA serum concentrations decreased notably 1 month after the onset of symptoms, but neutralizing IgA remained detectable in saliva for a longer time (days 49 to 73 post-symptoms). These results represent a critical observation given the emerging information as to the types of antibodies associated with optimal protection against reinfection and whether vaccine regimens should consider targeting a potent but potentially short-lived IgA response.

Secretory immunoglobulin A induces human lung fibroblasts to produce inflammatory cytokines and undergo activation

Immunoglobulin (Ig)A is the most abundant immunoglobulin in humans, and in the airway mucosa secretory IgA (sIgA) plays a pivotal role in first-line defense against invading pathogens and antigens. IgA has been reported to also have pathogenic effects, including possible worsening of the prognosis of idiopathic pulmonary fibrosis (IPF). However, the precise effects of IgA on lung fibroblasts remain unclear, and we aimed to elucidate how IgA activates human lung fibroblasts. We found that sIgA, but not monomeric IgA (mIgA), induced interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP)-1 and granulocyte-macrophage colony-stimulating factor (GM-CSF) production by normal human lung fibroblasts (NHLFs) at both the protein and mRNA levels. sIgA also promoted proliferation of NHLFs and collagen gel contraction comparable to with transforming growth factor (TGF)-β, which is involved in fibrogenesis in IPF. Also, Western blot analysis and real-time quantitative polymerase chain reaction (PCR) revealed that sIgA enhanced production of α-smooth muscle actin (α-SMA) and collagen type I (Col I) by NHLFs. Flow cytometry showed that NHLFs bound sIgA, and among the known IgA receptors, NHLFs significantly expressed CD71 (transferrin receptor). Transfection of siRNA targeting CD71 partially but significantly suppressed cytokine production by NHLFs co-cultured with sIgA. Our findings suggest that sIgA may promote human lung inflammation and fibrosis by enhancing production of inflammatory or fibrogenic cytokines as well as extracellular matrix, inducing fibroblast differentiation into myofibroblasts and promoting human lung fibroblast proliferation. sIgA's enhancement of cytokine production may be due partially to its binding to CD71 or the secretory component.

Lung Function, Inflammation, and Endothelin-1 in Congenital Heart Disease-Associated Pulmonary Arterial Hypertension

Background

Breathlessness is the most common symptom in people with pulmonary arterial hypertension and congenital heart disease (CHD‐APAH), previously thought to be caused by worsening PAH, but perhaps also by inflammation and abnormalities of lung function. We studied lung function and airway inflammation in patients with CHD‐APAH and compared the results with controls.

Methods and Results

Sixty people were recruited into the study: 20 CHD‐APAH, 20 CHD controls, and 20 healthy controls. Spirometry, gas transfer, whole body plethysmography and lung clearance index, 6‐minute walk distance, and medical research council dyspnea scoring were performed. Inflammatory markers and endothelin‐1 levels were determined in blood and induced sputum. The CHD‐APAH group had abnormal lung function with lung restriction, airway obstruction, and ventilation heterogeneity. Inverse correlations were shown for CHD‐APAH between medical research council dyspnea score and percent predicted peak expiratory flow (r=−0.5383, P=0.0174), percent predicted forced expiratory flow rate at 50% of forced vital capacity (r=−0.5316, P=0.0192), as well as for percent predicted forced expiratory volume in 1 s (r=−0.6662, P=0.0018) and percent predicted forced vital capacity (r=−0.5536, P=0.0186). The CHD‐APAH patients were more breathless with lower 6‐minute walk distance (360 m versus 558 m versus 622 m, P=0.00001). Endothelin‐1, interleukin (IL)‐β, IL‐6, IL‐8, tumor necrosis factor α, and vascular endothelial growth factor were significantly higher in CHD‐APAH than controls. Serum endothelin‐1 for CHD‐APAH correlated with airflow obstruction with significant negative correlations with percent predicted forced expiratory flow rate at 75% of forced vital capacity (r=−0.5858, P=0.0135).

Conclusions

Raised biomarkers for inflammation were found in CHD‐APAH. Significant abnormalities in airway physiology may contribute to the dyspnea but are not driven by inflammation as assessed by circulating and sputum cytokines. A relationship between increased serum endothelin‐1 and airway dysfunction may relate to its bronchoconstrictive properties.

Recognizing and differentiating uncommon body fluids: Considerations and tools for a proper practical approach

Clinical laboratories are regularly requested to inspect uncommon body fluids obtained from patients because clinicians are uncertain as to the origin of the collected material. They may need this information for the actual diagnosis, to confirm a supposition, or for guiding treatment and invasive operations like draining and puncturing. Often there is also a need to know more precisely what is going on in the cavity that gave rise to the fluid, for instance a local infection or metastasis, or whether the cavity is connected to organs or fluid compartments nearby etcetera. The results of the laboratory investigations often have () direct consequences. As the investigation of uncommon body fluids is distinct from routine laboratory analyses it requires special attention. This paper presents an overview of the characteristics of uncommon human body fluids, constituents useful as markers for recognizing and differentiating fluids and considerations that have to be taken into account when interpreting the results of analyses. In addition a number of practical recommendations for approaching the task of identifying uncommon body fluids are given.

Lung function in pulmonary hypertension

Breathlessness is a common symptom in pulmonary hypertension (PH) and an important cause of morbidity. Though this has been attributed to the well described pulmonary vascular abnormalities and subsequent cardiac remodelling, changes in the airways of these patients have also been reported and may contribute to symptoms. Our understanding of these airway abnormalities is poor with conflicting findings in many studies. The present review evaluates these studies for the major PH groups. In addition we describe the role of cardiopulmonary exercise testing in the assessment of pulmonary arterial hypertension (PAH) by evaluating cardiopulmonary interaction during exercise. As yet, the reasons for the abnormalities in lung function are unclear, but potential causes and the possible role of inflammation are discussed. Future research is required to provide a better understanding of this to help improve the management of these patients.

α-1-antitrypsin variants and the proteinase/antiproteinase imbalance in chronic obstructive pulmonary disease

The excessive activities of the serine proteinases neutrophil elastase and proteinase 3 are associated with tissue damage in chronic obstructive pulmonary disease. Reduced concentrations and/or inhibitory efficiency of the main circulating serine proteinase inhibitor α-1-antitrypsin result from point mutations in its gene. In addition, α-2-macroglobulin competes with α-1-antitrypsin for proteinases, and the α-2-macroglobulin-sequestered enzyme can retain its catalytic activity. We have studied how serine proteinases partition between these inhibitors and the effects of α-1-antitrypsin mutations on this partitioning. Subsequently, we have developed a three-dimensional reaction-diffusion model to describe events occurring in the lung interstitium when serine proteinases diffuse from the neutrophil azurophil granule following degranulation and subsequently bind to either α-1-antitrypsin or α-2-macroglobulin. We found that the proteinases remained uninhibited on the order of 0.1 s after release and diffused on the order of 10 μm into the tissue before becoming sequestered. We have shown that proteinases sequestered to α-2-macroglobulin retain their proteolytic activity and that neutrophil elastase complexes with α-2-macroglobulin are able to degrade elastin. Although neutrophil elastase is implicated in the pathophysiology of emphysema, our results highlight a potentially important role for proteinase 3 because of its greater concentration in azurophil granules, its reduced association rate constant with all α-1-antitrypsin variants studied here, its greater diffusion distance, time spent uninhibited following degranulation, and its greater propensity to partition to α-2-macroglobulin where it retains proteolytic activity.

A mathematical model to predict protein wash out kinetics during whole-lung lavage in autoimmune pulmonary alveolar proteinosis

Whole-lung lavage (WLL) remains the standard therapy for pulmonary alveolar proteinosis (PAP), a process in which accumulated surfactants are washed out of the lung with 0.5-2.0 l of saline aliquots for 10-30 wash cycles. The method has been established empirically. In contrast, the kinetics of protein transfer into the lavage fluid has not been fully evaluated either theoretically or practically. Seventeen lungs from patients with autoimmune PAP underwent WLL. We made accurate timetables for each stage of WLL, namely, instilling, retaining, draining, and preparing. Subsequently, we measured the volumes of both instilled saline and drained lavage fluid, as well as the concentrations of proteins in the drained lavage fluid. We also proposed a mathematical model of protein transfer into the lavage fluid in which time is a single variable as the protein moves in response to the simple diffusion. The measured concentrations of IgG, transferrin, albumin, and β2-microglobulin closely matched the corresponding theoretical values calculated through differential equations. Coefficients for transfer of β2-microglobulin from the blood to the lavage fluid were two orders of magnitude higher than those of IgG, transferrin, and albumin. Simulations using the mathematical model showed that the cumulative amount of eliminated protein was not affected by the duration of each cycle but dependent mostly on the total time of lavage and partially on the volume instilled. Although physicians have paid little attention to the transfer of substances from the lung to lavage fluid, WLL seems to be a procedure that follows a diffusion-based mathematical model.

Essential role of factor B of the alternative complement pathway in complement activation and opsonophagocytosis during acute pneumococcal otitis media in mice

We recently reported that the complement system plays a pivotal role in innate immune defense against Streptococcus pneumoniae during acute otitis media (OM) in mice. The current study was designed to determine which of the complement pathways are activated during acute pneumococcal OM and whether components of complement are expressed in the middle ear epithelium. Gene expression was determined by quantitative PCR, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence staining. We found that S. pneumoniae induced increased gene expression of factor B of the alternative complement pathway and C3 in mouse middle ear epithelium. Activation of factor B and C3 in the middle ear lavage fluids was significantly greater than in simultaneously obtained serum samples as determined by Western blotting. Using mice deficient in complement C1qa, factor B, and factor B/C2, we found that complement C3 activation and opsonophagocytosis of S. pneumoniae were greatly attenuated in factor B- and factor B/C2-deficient mice. These findings support the concept that local complement activation is an important host innate immune response and that activation of the alternative complement pathway represents one of the innate immune defense mechanisms against pneumococcal infection during the early stage of acute OM.

Airway inflammation in nonobstructive and obstructive chronic bronchitis with chronic haemophilus influenzae airway infection. Comparison with noninfected patients with chronic obstructive pulmonary disease

Nonencapsulated Haemophilus influenzae often causes chronic infections of the lower respiratory tract in both nonobstructive and obstructive chronic bronchitis. We assessed airway inflammation in clinically stable, chronically H. influenzae-infected patients with nonobstructive (CB-HI, n = 10) and in patients with obstructive chronic bronchitis (COPD-HI, n = 10) by analyses of the sol phase of spontaneously expectorated sputum (SSP). As compared with the CB-HI group, the COPD-HI group had significantly higher (p < 0.05) levels of myeloperoxidase (MPO) and tumor necrosis factor (TNF)-alpha in their SSP, whereas the degree of plasma protein leakage (SSP-to-serum ratio of plasma proteins) and the levels of interleukin (IL)-8, secretory IgA, and lactoferrin were similar in the two groups. These findings point to differences in pathophysiology in CB-HI and COPD-HI. The high level of TNF-alpha in the SSP of COPD-HI patients is in accord with the proposed role of TNF-alpha in the development of airway obstruction in COPD patients. In apparent contradiction, low levels of TNF-alpha were found in the SSP of noninfected but otherwise similar COPD patients (n = 9). This finding, however, does not exclude an exaggerated TNF-alpha response to infection or another stimulus in the airways of COPD patients. The SSP levels of MPO and IL-8, and the degree of plasma protein leakage in the COPD-HI group, were retrospectively compared with and found significantly higher than those of noninfected COPD patients, suggesting a more marked inflammatory response in COPD-HI. Whether this reflects a direct cause-and-effect relationship should be addressed in a future long-term prospective study involving repeated measurements in the same patients.

IgG subclasses in the serum and sputum from patients with bronchiectasis

BACKGROUND

IgG subclass deficiency is often associated with recurrent pulmonary infections. The prevalence of deficiency in a large well characterised group of patients with bronchiectasis has not previously been established.

METHODS

Serum IgG subclass concentrations in 89 patients with bronchiectasis were compared with those obtained from a group of 82 age and sex matched normal healthy controls. Sputum IgG subclass concentrations were also assessed in 44 of the patients. Albumin was measured as a marker of protein transudation from plasma to determine the degree of local IgG subclass production.

RESULTS

The serum concentrations of IgG1, IgG2 and IgG3 were increased in the patients compared with the control group whereas IgG4 concentrations were not. There was an overall incidence of deficiency of 1% for subclasses 1-3 and 5% for subclass 4 in patients with bronchiectasis based on observed concentrations being below the lower limit of the control group range. The concentrations of IgG subclasses in sputum were partly dependent upon the degree of inflammation as assessed by the macroscopic appearance of purulence. A comparison of the ratio of sputum:serum subclass concentration and sputum:serum albumin, however, revealed that all of the subclasses were present at greater concentrations than could be accounted for by transudation alone.

CONCLUSIONS

A new normal control range for serum IgG subclasses has been established and from this range it was found that IgG subclass deficiency in a group of unselected patients with bronchiectasis was comparatively rare. A significant degree of local IgG production was also suggested in the lungs of these patients.

Plasma protein leakage and local secretion of proteins assessed in sputum in asthma and COPD. The effect of inhaled corticosteroids

Asthma and chronic obstructive pulmonary disease (COPD) are characterized by chronic airway inflammation with cell infiltration, increased plasma exudation and abnormal local secretion of proteins. We have analysed whether sputum differs in this respect between asthma (n = 9) and COPD (n = 9), and whether inflammatory markers in sputum are affected by treatment. In non-smoking asthma patients there was more plasma protein leakage, based on the relative coefficient of excretion Q alpha 2macroglobulin/QIgG (P = 0.03). There was less local secretion of sIgA and lactoferrin than in COPD (P < 0.05). Tryptase was slightly higher in sputum from asthma than from COPD (P < 0.05), whereas eosinophil cationic protein and myeloperoxidase were similar. After treatment with glucocorticosteroids, there was a reduction in the Q alpha 2macroglobulin/Qalbumin (P < 0.015), but no effect was seen on the levels of products from local cells. We conclude that sputum analysis is useful to study the local inflammatory process in asthma and COPD.

Defensins reduce the barrier integrity of a cultured epithelial monolayer without cytotoxicity

Polymorphonuclear leukocytes (PMN) contribute to epithelial injury at sites of inflammation, but their mechanisms of action are incompletely understood. PMN can injure target tissues by oxidative and nonoxidative mechanisms. Included in the nonoxidative mechanisms are defensins (DEF), small (3.5 to 4.0 kD), arginine- and cysteine-rich polypeptides. DEF are bactericidal, fungicidal, viricidal, and tumoricidal, but their ability to contribute to inflammatory injury has not been extensively evaluated. One marker of inflammatory injury is disrupted epithelial barrier integrity. Using Madin-Darby canine kidney (MDCK) epithelial monolayers, we measured the effect of both human and rabbit DEF on barrier integrity using mannitol permeability (Pmann) and transepithelial electrical resistance (Rt). Human DEF (HNP1-3, 2:2:1 molar ratio) increased Pmann in a time- and concentration-dependent manner and Rt fell progressively over a 48-h period after exposure of monolayers to HNP1-3. Rabbit DEF peptide 1 (NP-1) also increased Pmann, but rabbit peptide 5 (NP-5) had no effect on Pmann. To investigate the role of charge, HNP1-3 was added to the monolayers with the polyanions heparin or sulfated dextran. Heparin and sulfated dextran only partially inhibited the increase in Pmann. Fetal bovine serum (FBS), however, completely inhibited the effect of HNP1-3, but this protection was only partially explained by the anionic protein, albumin. The FBS protection was time dependent and was present when FBS was added up to 16 h after exposure to HNP1-3. While both HNP1-3 and NP-1 increased epithelial permeability, neither were cytolytic to MDCK cells as measured by lactate dehydrogenase release.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of an enzyme-linked immunosorbent assay to assess penetration of amoxicillin into lung secretions

An enzyme-linked immunosorbent assay (ELISA) was developed to measure total amoxicillin concentrations penetrating lung secretions, which were compared with "active" concentrations measured by conventional bioassay. An antibody was raised in rabbits to amoxicillin conjugated to bovine serum albumin and used in a competitive binding ELISA (sensitivity, 10 ng/ml; precision [coefficient of variation], 9%). The measurement of amoxicillin in lung secretions by using the ELISA method was verified by high-performance liquid chromatography. Amoxicillin concentrations were found to be similar in both whole sonicated sputum and sol-phase sputum obtained by ultracentrifugation following single oral doses of 3 g (4.6 mg/liter for sonicated and 4.7 mg/liter for sol-phase preparations) and 250 mg (0.23 mg/liter for both preparations). Eight patients with bronchiectasis received 500 mg of amoxicillin three times daily. On the second day of therapy (4 h after the morning dose), the mean concentration of amoxicillin in sputum was 0.88 mg/liter (standard error of the mean [SEM], 0.11) by ELISA and 0.40 mg/liter (SEM, 0.05) by bioassay, suggesting a significant degree of local inactivation. This difference between total and active amoxicillin levels was found to correlate significantly (r = 0.693; P less than 0.05) with beta-lactamase levels (mean, 29.5 mU/ml; SEM, 9.4). A pharmacokinetic study on day 3 revealed maximum levels in secretions 2 to 4 h after dosing (mean, 1.36 mg/liter; SEM, 0.26). At the end of successful therapy (day 14), total and active levels were lower (mean, 0.48 mg/liter; SEM, 0.11 [total]; mean, 0.21 mg/liter; SEM, 0.06 [active]); this result was associated with a reduction in lung inflammation (decreased serum-derived albumin in the lung secretions). In conclusion, antibiotic penetration is partly dependent on the degree of lung inflammation. The differences observed in total and active levels of amoxicillin and the relationship to beta-lactamase activity in sputum suggest why higher doses of antibiotic may be required to produce a therapeutic response in some patients.

Sputum sol phase proteins and elastase activity in patients with clinically stable bronchiectasis

BACKGROUND

Inflammatory and proteolytic activity occurs in sputum from patients with stable purulent bronchiectasis and has been proposed as the main pathogenetic mechanism of the disease. This study was designed to define further the role of inflammation and proteolysis in bronchiectasis.

METHODS

Neutrophil elastase activity, sputum concentrations of the serum derived inhibitors alpha 1 antiproteinase and alpha 2 macroglobulin, and the sputum to serum ratios of albumin and C reactive protein concentration were measured in 26 patients with bronchiectasis.

RESULTS

Free elastase activity was found in 15 sputum samples. A trend to higher proteolytic and inflammatory activity was found between mucoid and purulent sputum samples, suggesting that inflammatory and proteolytic activities are related to the macroscopic degree of purulence. Purulent sputum had a high sputum to serum ratio of C reactive protein, suggesting local production or active transport of this protein into bronchial secretions. C reactive protein was more sensitive than albumin in detecting a higher degree of inflammation in elastase positive samples.

CONCLUSION

The finding of greater concentrations of alpha 2 macroglobulin in purulent and elastase positive samples than in mucopurulent, mucoid and elastase negative sputum samples suggests that this inhibitor may have a role in the proteolysis-antiproteolysis balance in bronchial secretions.

Influx of urea during bronchoalveolar lavage depends on the permeability of the respiratory membrane

In 6 healthy controls and 23 patients with pulmonary diseases the influx of urea during bronchoalveolar lavage was measured by comparing the concentrations of albumin and urea in the sequential samples recovered. It varied between -28 and 151 mumol/l. In the bronchoalveolar lavage fluid and serum we measured alpha-2-macroglobulin (A2M) and ceruloplasmin (CP). The bronchoalveolar lavage fluid to serum ratios were calculated (QCP and QA2M). QA2M/QCP was taken as a measure of the respiratory membrane permeability; it varied between 0.05 and 0.53. Influx of urea during lavage was higher according as the QA2M/QCP ratio was higher. We conclude that concentrations of substances in the epithelial lining fluid calculated with the urea correction method have to be corrected for the influx of urea.

IgA subclasses in sputum from patients with bronchiectasis

The concentrations of IgA1 and IgA2 were measured in the serum and sputum from 27 clinically stable patients with bronchiectasis. Of the 27 patients, nine were regularly producing mucoid secretions, nine mucopurulent and nine purulent secretions. No significant differences were observed in serum IgA2 concentrations between the patient groups, although IgA1 concentrations were higher in the serum from the patients producing mucopurulent sputum than those producing mucoid or purulent sputum. The sputum concentrations of both IgA1 and IgA2 increased significantly with purulence. Furthermore, there was a significant increase in the proportion of IgA2 as the secretions became more purulent. The sputum concentrations of both IgA subclasses indicated significant local synthesis, with increased production (especially of IgA2) in the presence of inflammation due to infection.

The measuring of "respiratory-membrane permeability" and local production of immunoglobulins and antibodies by means of an analysis of sputum

When measuring the exudation of serum proteins and the local production of immunoglobulins and antibodies within the lung by means of an analysis of sputum, the permeability properties of the respiratory membrane should be taken into account. In this paper, we describe the "loss of size selectivity" that usually accompanies an increased permeability on the part of the respiratory membrane. This phenomenon enables us to measure respiratory membrane permeability independently of the sputum water content. Consequences with regard to discrimination between leakage from the circulation and/or local production of immunoglobulins and antibodies are discussed. Sequential studies which take these factors into account may provide insights into the extent of local inflammatory reactions in individual patients.

Assessment of soluble parameters in sputum

The concentrations of soluble protein in lung secretions are dependent upon the degree of inflammation, local production and cell activation. Infections and corticosteroid therapy will alter the protein content of lung secretions as a result of their effect on lung inflammation.

Exudative indices in airways inflammation

Airways inflammation has come to be equated with the presence of inflammatory cells and their products in airway lumen and tissue. However, the inflammatory condition must also, or rather, be determined by indices which show to what degree the tissue itself is affected by the process. Plasma exudation from abundant subepithelial microvessels is a specific defence/inflammatory tissue response to mucosal provocations; promptly after extravasation, the plasma exudate reversibly and non-injuriously creates intercellular pathways across the mucosa; the exudate enters the airway lumen without compromising the epithelial lining as a barrier to luminal solutes; there is a good correlation between surface and tissue plasma exudates. I propose that plasma tracers on the mucosal surface can identify the ongoing airway inflammation, its intensity and time-course in great detail.

Humoral immune responses within the lung of bone marrow transplant recipients studied by bronchoalveolar lavage

We investigated 20 bone marrow transplant recipients with pneumonitis using bronchoalveolar lavage (BAL) to assess the humoral immune response in the lung. We measured the levels of total IgG, IgM and IgA in bronchoalveolar lavage fluid and serum, and albumin measurements were used to correct for simple diffusion of immunoglobulins from serum into the lung. We found evidence for the local production of immunoglobulins G, M and A in 15 patients. This was independent of the cause of the pneumonitis. We also found that, although seven patients who recovered from their pulmonary problem had evidence of considerable local production of immunoglobulin, eight patients who died were also producing immunoglobulins in the lung. Death due to pneumonitis in BMT recipients cannot, therefore, be ascribed to a failure of the local humoral immune response.

Plasma exudation and asthma

Several pieces of evidence support the view that exudation of plasma into the airway wall and into the airway lumen occurs in asthma. Vascular leakage of plasma results from inflammatory mediator-induced separation of endothelial cells in postcapillary venules belonging to the tracheobronchial circulation. Whereas proposed mediators of asthma induce reversible leakage, several antiasthma drugs exhibit antileakage effects in animals and humans. Potential consequences of plasma exudation are many. Mucosal/submucosal edema might contribute to airway hyperresponsiveness. Plasma exudate in the airway lumen in asthma may contribute to sloughing of epithelium, impairment of mucociliary transport, narrowing of small airways, and mucus plug formation. Exuded plasma may cause airway inflammation and constriction because of its content of powerful mediators, and chemoattractant factors and plasma proteins may condition the inflammatory cells abundant in asthmatic airways to release mediators in response to stimuli that otherwise would be innocuous to the cells. It is concluded that inflammatory stimulus-induced increase in macromolecular permeability of the tracheobronchial microvasculature and mucosa may be a significant pathogenetic mechanism in asthma and that the postcapillary venular endothelium and airway epithelium that regulate leakage of plasma are important effector cells in this disease.

Cells containing IgA subclasses in bronchi of subjects with and without chronic obstructive lung disease

Necropsy specimens were obtained from the lungs of 10 subjects who had no history of lung disease, 10 who had died with chronic bronchitis, and 10 with bronchiectasis. Tissue sections were stained for IgA1 or IgA2 using the immunoperoxidase technique, and the number of cells in the bronchi stained for these proteins was counted. The total number of IgA positive cells was increased in bronchitic and bronchiectatic lungs compared with those from control subjects. The number of IgA2 positive cells was similar in those with bronchitis and bronchiectasis and significantly higher than in controls. Similarly, cells containing IgA1 were increased in the lungs of subjects with chest disease but were higher in those with bronchitis than in those with bronchiectasis. The proportion of IgA2:total IgA containing cells was similar in sections from controls (mean (SD) 25 (5.0)%) and those with bronchiectasis (mean (SD) 24 (4)%), but lower in those with bronchitis (mean (SD) 19 (5.0)%). The results show that cells containing IgA1 predominate in the major bronchi but that the proportion of cells containing IgA2 is higher than in non-mucosal lymphoid tissues. Bronchitis and bronchiectasis are associated with greater numbers of cells producing IgA in the bronchi, and this is consistent with increased local production of IgA in the lung secretions of bronchitic subjects.

Concentration of bronchoalveolar lavage fluid by ultrafiltration: evidence of differential protein loss and functional inactivation of proteinase inhibitors

Bronchoalveolar lavage samples were concentrated using positive-pressure ultrafiltration. The starting material, concentrates, and eluates were assayed for immunoglobulin A (IgA), albumin (Alb), alpha 1-proteinase inhibitor (alpha 1-PI), antileukoprotease (ALP), and total leukocyte elastase inhibitory capacity (LEIC). No enzyme inhibitory capacity or protein was detected in membrane eluates, confirming the selectivity of the membrane used (Mr cutoff 2000 or 500). However, the concentrated lavages showed a generated loss of protein. The proportion of each protein recovered using the 500 Mr cutoff membrane was: IgA, 50.6% (+/- 15%); albumin, 43% (+/- 8.4); alpha 1-PI, 53.6 (+/- 17.3); ALP, 43% (+/- 2.1); and LEIC, 18.4% (+/- 2.6). Similar results were obtained with the 200 Mr cutoff membrane. The alpha 1-PI/Alb and the IgA/alb ratios were higher (2P less than 0.05) in the concentrates than in the starting material, suggesting differential protein loss. Protein losses were due to binding to the membrane since the wash with saline solution improved recoveries: IgA, 80%; Alb, 56%; alpha 1-PI, 64%; ALP, 66%; LEIC, 29%. Concentration of bronchoalveolar lavage fluids therefore resulted in substantial differential losses in elastase inhibitory capacity and protein concentrations, suggesting analysis of these fluids should be performed on unconcentrated samples.

Elastolytic activity of sputum and its relation to purulence and to lung function in patients with bronchiectasis

Sputum samples from 34 patients with bronchiectasis were assessed subjectively and the results related to objective measurements of elastase activity and albumin content. The results suggest that the macroscopic appearance of the sample is related to the elastase content. 88.7% of the purulent samples but none of the mucoid samples showing elastase activity. The macroscopic appearance was also associated with changes in protein transudation into the secretions. The median sputum: serum albumin concentration ratio was 0.71 X 10(-2) (range 0.22-4.7) in the mucoid samples but was greater in purulent samples (p less than 0.005), with a median value of 1.52 X 10(-2) (range 0.55-12.72), suggesting that purulence in the stable state was associated with low grade pulmonary inflammation or epithelial damage or both. Abnormalities of air flow were found in 24 of the patients (70.6%) but there was a significantly higher ratio of residual volume to total lung capacity (p less than 0.025) in patients who regularly produced purulent sputum (mean (SD) RV/TLC 44.4% (9.0%] than in those with mucoid or mucopurulent secretions (38.0% (9.9%]. A similar difference was found between those who produced elastase positive secretions and those who produced elastase negative ones.

The secretory IgA system of lung secretions in chronic obstructive bronchitis: comparison of sputum with secretions obtained during fibreoptic bronchoscopy

The constituents of the secretory immunoglobulin A system (dimeric IgA, total secretory component and free secretory component) were measured in sputum sol phase, tracheal aspirates, and bronchoalveolar lavage fluids from 15 patients undergoing fibreoptic bronchoscopy. All of the proteins showed a progressive decrease in concentration from sputum to the bronchoalveolar lavage fluids (2p less than 0.001). Standardisation of samples by means of protein concentration ratios showed that all secretions were generally similar in respect of their secretory IgA profiles, although major differences remained in some individual patients. The between patient variability of the results was generally reduced by the use of protein concentration ratios, allowing closer comparison between subjects. When the secretion albumin concentration was used as a standard, however, it increased the variability of the sputum sol phase IgA components (2p less than 0.01), whereas it decreased the variability of the IgA components in the bronchoalveolar lavage fluid (2p less than 0.05). The role of albumin as a standard protein for assessing the secretory IgA system in lung secretions remains uncertain.

Effect of antibiotic treatment on sputum elastase in bronchiectatic outpatients in a stable clinical state

Broad spectrum antibiotic treatment was given on 21 occasions to 15 patients with bronchiectasis who regularly produced purulent, elastase positive secretions. Although the results showed that sputum clearing--that is, changing from purulent to mucoid--largely depended on the pathogenic organism isolated, this was not exclusively the case and in some cases sputum growing sensitive organisms failed to clear whereas clearing occurred in other samples containing resistant organisms or no obvious pathogens. Clearing of sputum was achieved eventually in 12 of the patients and this was associated with the disappearance of elastase activity, although it returned in 10 patients within one week of stopping treatment. There was no change in sputum elastase where the sputum failed to clear. The clearance of elastase activity was associated with a decrease in protein transudation into the lung secretions. The sputum:serum albumin concentration ratio fell (p less than 0.005) from a mean (SD) of 2.32 (1.56) X 10(-2) in these 12 patients before treatment to 1.09 (0.40) X 10(-2) within the first week of treatment, but rose again to 2.07 (1.29) X 10(-2) within one week of stopping treatment. The results suggest that antibiotic treatment when patients are in a stable state may have a beneficial effect on the pathogenic nature of lung secretions and inflammation within the lung.

Bacteriological and biochemical criteria for the diagnosis of bacterial infections in chronic obstructive pulmonary disease (COPD)

In a prospective study the quantitated culture of washed sputum, the number of leukocytes and the concentration of albumin and fibrinogen in sputum were compared as diagnostic parameters for bacterial infections in patients with chronic obstructive pulmonary disease. No single criterium and no combination of criteria showed satisfactory specificity and sensitivity. Two reasons were established for the relatively loose correlation between the parameters: 1) they follow a different time course and 2) the biochemical and cellular signs of inflammation have a certain non-specificity with regard to bacterial infections. They also depend on the underlying disease. The selection of optimal criteria will become feasible only after the dynamics of bacterial and other inflammations of the respiratory tract have been studied in detail.

Action of serum on the output of secretory glycoproteins from human bronchi in vitro

The effect on mucin output of placing dilute serum from healthy donors in contact with the luminal surface of human airway has been studied. Bronchi were dissected from lungs removed at operation. Mucins, radiolabelled biosynthetically, were collected from the luminal aspect of the bronchi, which were mounted in Ussing chambers. Serum added to the luminal aspect of the tissue, at dilutions ranging from 1:100 to 1:10 of Krebs-Henseleit solution, consistently increased the output of radiolabelled mucins. The concentrations of serum tested in these experiments lie within the range commonly found in sputum coughed from the lungs of those with inflamed airways. Serum diluted to 1:2500, which is roughly the concentration found in the normal human airway, had little or no effect on bronchial secretion. Increased leakage of serum into the inflamed airways is suggested as one of the stimuli that increase bronchial secretion.

Pulmonary oedema and chronic bronchitis associated with perioperative sepsis

The relationship of pulmonary oedema and chronic bronchitis in perioperative septic patients has been examined. There is a close association. It appears likely that the reason for this association is a reduction of the pulmonary vascular capacity due to destructive changes, hypertrophy of muscle within the walls of blood vessels and widespread regional hypoxic pulmonary vasoconstriction.

Lung secretion sol-phase proteins: comparison of sputum with secretions obtained by direct sampling

The protein content of tracheal secretions and of bronchial lavage and bronchoalveolar lavage fluid was compared with that of sputum in 33 patients who underwent fibreoptic bronchoscopy. The secretion-to-serum concentration ratios for albumin, alpha 1-antitrypsin, alpha 1-antichymotrypsin, and immunoglobulin A (IgA) fell progressively as samples were obtained from further down the bronchial tree, probably reflecting greater sample dilution. The secretion-to-serum protein ratios when standardised for the corresponding albumin ratio were similar in all secretions studied. In particular, the IgA ratios were about eight times those of albumin and alpha 1-antichymotrypsin ratios were about twice those of albumin, suggesting similar degrees of "local production" of these proteins in all secretions studied. Some patients showed considerable differences in IgA ratios between sputum and bronchial lavage fluid. The significance of these differences is not clear.

Effect of corticosteroids on sputum sol-phase protease inhibitors in chronic obstructive pulmonary disease

Corticosteroids caused a reduction in the ratio of sol-phase sputum concentration to serum concentration of albumin in 12 patients with chronic obstructive bronchitis, suggesting a reduction in protein transudation. Alpha-1-antitrypsin values followed the same pattern as those of albumin in both the control and treatment periods, confirming the similar behaviour of the two proteins. The alpha 1-antichymotrypsin ratios were on average three times higher than those of albumin in the control period, confirming the presence of local mechanisms in the lung for preferentially concentrating this protein. The sputum-to-serum ratio of alpha 1-antichymotrypsin, however, rose during steroid treatment with the result that there was a selective increase in this protease inhibitor, which may be of potential benefit to such patients.

Serum and sputum alpha 2 macroglobulin in patients with chronic obstructive airways disease

Serum alpha 2 macroglobulin concentrations were measured in patients with chronic obstructive airways disease and an age-matched group of control subjects. The mean serum level of alpha 2 macroglobulin was significantly lower in bronchitic subjects with acute chest infections than the mean value of the controls. No significant differences were observed between serum alpha 2 macroglobulin values in controls, subjects with "emphysema", and bronchitic patients who did not have chest infections. Sputum alpha 2 macroglobulin concentrations were compared in sputum samples from bronchitic patients with and without acute chest infections. The protein was detected (greater than 0.2 mg/l) in 94% of sputum samples from infected subjects but only 60% of non-infected sputum samples. Concentrations of alpha 2 macroglobulin in infected samples were significantly higher than the non-infected samples. Sputum/serum concentration ratios of alpha 2 macroglobulin were also significantly higher in infected samples but this difference was eliminated by "correcting" the values with the albumin sputum/serum ratios of the same samples. The results suggest that alpha 2 macroglobulin concentrations are higher in bronchial secretions during chest infection because of increased transudation from the blood rather than the presence of significant local secretion.

The immunological measurements of 'free' secretory piece and its relationship to local IgA production

Free secretory piece (FSP) was studied in the sputum of patients with chronic bronchitis. The concentrations were higher both in the presence of infection and when greater quantities of total secretory piece were present compared to the amount of 11S IgA. A significant inverse correlation was found between the amount of FSP and 11S IgA in the individual samples when standardized for their total secretory piece content (2P less than 0 . 01). This suggests that the amount of FSP in any sample is partly dependent upon the amount of 11S IgA. The techniques employed offer a method for the study of the secretory IgA system in biological fluids. The preliminary results suggest that the secretory IgA system is independent of the systemic IgA system.

A method for the study of local IgA production using radial immunodiffusion and thin layer chromatography

A technique is described for the assessment of local IgA production in external secretions variably contaminated with serum IgA. The combination of total IgA and secretory piece measurements by radial immunodiffusion and 11S and 7S IgA measurements by thin layer gel chromatography provide information concerning local IgA and its association with secretory piece.

Local IgA production in patients with chronic bronchitis: effect of acute respiratory infection

The immunoglobulin A and secretory IgA concentrations were studied in the serum and sputum of patients with chronic bronchitis to determine the effect of active chest infection and inflammation upon the estimation of local IgA production. The sputum/serum albumin ratio was higher during chest infection (5.51; SE+/-1.60x10(-2)) than in the non-infected samples (0.75; SE+/-0.14x10(-2);p less than 0.01) suggesting increased transudation as a result of inflammation. There was a similar increase in sputum/serum IgA during infection from 9.47 (SE+/-1.87)x10(-2) to 41.21 (SE+/-6.92)x10(-2)(p less than 0.01). However, the proportion of IgA locally produced when assessed by conventional techniques was unchanged. There was a significant inverse relationship between the estimated local IgA production of the infected samples and the degree of inflammation (r= -0.972;2p less than 0.001) indicating that inflammation was a major determinant of local IgA production. However, the secretory IgA concentrations of the samples were independent of the degree of inflammation. Furthermore, secretory IgA was found in samples that appeared to have failure of local IgA production using the method of Soutar. Clearer information about local IgA production can be obtained by measuring protein components unique to the bronchial secretions rather than applying correction factors to estimate the contribution of serum components, particularly in the presence of inflammation.