Elevated levels of leukotriene C4 in bronchoalveolar lavage fluid from atopic asthmatics after endobronchial allergen challenge

Sulfidopeptide leukotrienes have been implicated in the pathogenesis of asthma because of their ability to induce bronchospasm, airways hyperreactivity, and increased mucus production. In the present study, the leukotrienes (LT) C4, D4, and E4 were measured in bronchoalveolar lavage fluid (BALF) before and 5 min after endobronchial allergen challenge in four subject groups: nonatopic nonasthmatic, nonatopic asthmatic, atopic nonasthmatic, and atopic asthmatic. As determined by high performance liquid chromatography (HPLC), after allergen challenge, the predominant sulfidopeptide leukotriene found in BALF from atopic asthmatics was LTC4. Smaller amounts of LTD4 and LTE4 were detectable. The baseline level of leukotrienes in the atopic asthmatics was 64 +/- 18 pg/ml, with measurable levels being found in nine of 11 samples. Atopic nonasthmatics had measurable levels in only one of seven baseline samples, whereas five of six nonatopic subjects had undetectable levels. Allergen challenge in atopic asthmatics resulted in significant increases in LTC4 over prechallenge levels (64 +/- 18 to 616 +/- 193 pg/ml) (p less than 0.01) and over levels in the three control groups after challenge (p = 0.0297). The atopic nonasthmatic group also had detectable leukotriene levels after allergen challenge (88 +/- 32 pg/ml), whereas leukotrienes remained undetectable in five of the six nonatopic samples. For comparison, histamine and the prostanoids prostaglandin D2 (PGD2) and thromboxane B2 (TxB2) were also measured in BALF. The levels of all three of these mediators increased in BALF from atopic asthmatics after allergen challenge. After allergen challenge, the best correlation was found between the levels in BALF for the prostanoids PGD2 and TxB2 (r = 0.88).(ABSTRACT TRUNCATED AT 250 WORDS)     

Elevated prostaglandin E2 levels in bronchoalveolar lavage fluid of patients with bronchogenic carcinoma

Understanding local pulmonary immunoregulatory mechanism(s) in patients with carcinoma of the lung is an important step towards the development of innovative methods of treatment. Prostaglandin E2 plays an integral role in immunoregulation. Therefore, we evaluated PGE2 concentrations in BALF from 18 patients with bronchogenic carcinoma, compared to that from six patients with pulmonary diseases other than carcinoma and ten normal smokers of similar age. The level of PGE2 in patients with lung carcinoma (158.1 +/- 88.7 pg/ml) was significantly (p less than 0.001) higher than the other two groups (16.2 +/- 6.9 and 4.4 +/- 3.4 pg/ml). Levels of PGE2 also varied among patients with carcinoma of different cell types. Patients with SQCA had significantly (p less than 0.001) higher levels of PGE2 (242.7 +/- 29.4 pg/ml) than patients with ADCA or SCCA (82.3 +/- 27.9 and 66.3 +/- 15.2 pg/ml, respectively). Furthermore, there was a marked difference in PGE2 concentration between carcinomatous lung and clinically noninvolved lung in patients with SQCA and ADCA. Further study is warranted to determine the interactions between PGE2 and other cytokines (interleukin-1, IL-2, and tumor necrosis factor), as well as the activity of cytolytic lymphocytes (LAK cells) in the lungs of patients with bronchogenic carcinoma.     

Elevated levels of thymus- and activation-regulated chemokine in bronchoalveolar lavage fluid from patients with eosinophilic pneumonia

Thymus- and activation-regulated chemokine (TARC/CCL17) is a lymphocyte-directed CC chemokine, which plays a role in the recruitment of CC chemokine receptor-4 positive T helper 2 (Th2) cells. In this study, we measured concentrations of TARC and Th2 cell-derived cytokines in bronchoalveolar lavage (BAL) fluid, as well as TARC concentrations in serum from patients with eosinophilic pneumonia and other interstitial lung diseases. TARC was significantly elevated in BAL fluids from patients with eosinophilic pneumonia (median, 240 pg/ml), whereas TARC was undetectable (< 7 pg/ml) in most cases of hypersensitivity pneumonitis, sarcoidosis, and idiopathic pulmonary fibrosis, as well as in healthy control subjects. Also, when present, quantities were less than 20 pg/ml. Elevated concentrations of interleukin (IL)-4, IL-5, and IL-13 were also detected in BAL fluid from patients with eosinophilic pneumonia. Interestingly, TARC concentrations in BAL fluids were closely correlated with the concentrations of IL-5 and IL-13. A serial examination showed that elevated TARC in BAL fluid rapidly fell to below detectable limits preceding decreases in IL-5 concentration and eosinophil percentage. Our results, in concordance with previous studies, demonstrate the potential activity of TARC for recruiting Th2 cells to the lungs and suggest a significant role for TARC in the pathogenesis of eosinophilic pneumonia.     

Interstitial lung disease in scleroderma. Immune complexes in sera and bronchoalveolar lavage fluid

Interstitial lung disease is a common feature of scleroderma (systemic sclerosis), and it may be a major determinant of morbidity and mortality. Analysis of bronchoalveolar lavage fluid from patients with scleroderma has shown evidence of inflammation in the lower respiratory tract of many patients. We have analyzed sera and bronchoalveolar lavage fluid from scleroderma patients for the presence of immune complexes, which may play a role in the inflammatory process. Using a solid-phase C1q enzyme-linked immunosorbent assay, we detected immune complexes in the sera of 6 of 23 patients (26%) and in none of 32 controls (P less than 0.01). All 6 patients with serum immune complexes had inflammatory cells in bronchoalveolar lavage fluid, and the presence of serum immune complexes correlated with the percentage of neutrophils in lavage fluid (P less than 0.02). Immune complexes were detected in lavage fluid of 11 of 21 patients (52%) compared with 1 of 7 normal controls (14%). Subjects having immune complexes in lavage fluid had a lower forced vital capacity than did those without lavage fluid immune complexes (P less than 0.05). The levels of immune complexes in bronchoalveolar lavage fluid exceeded those in serum by a mean of 45-fold, suggesting either local formation or selective deposition of immune complexes in the lower respiratory tract of some scleroderma patients.     

Interstitial lung disease in scleroderma analysis by bronchoalveolar lavage

Interstitial pulmonary fibrosis is a common feature of scleroderma (systemic sclerosis) which may result in impairment of pulmonary function and may be a major determinant of morbidity and mortality. Clinicopathologic observations suggest that interstitial and alveolar inflammation may appear prior to fibrosis. Using the bronchoalveolar lavage (BAL) technique, we have characterized the nature of the inflammatory process in the lower respiratory tracts of 19 nonsmoking scleroderma patients. Eleven of 19 patients (58%) had increased percentages of neutrophils and/or eosinophils in BAL fluid. Five of 10 patients (50%) had elevations of IgG in BAL fluid. The presence of neutrophils was associated with a decreased lung diffusing capacity for carbon monoxide (P < 0.05) and with more advanced radiographic features of interstitial fibrosis in patients with disease of more than 1 year's duration. This study suggests that scleroderma lung involvement may be characterized by an inflammatory alveolitis and that the presence of such inflammation may relate to the severity of the pulmonary disease.     

Evaluation and management of scleroderma lung disease using bronchoalveolar lavage

PURPOSE: Bronchoalveolar lavage (BAL) was performed in 43 nonsmoking patients with scleroderma (systemic sclerosis) to determine the frequency of alveolitis, the status of BAL findings over time, and the relationship of such findings to pulmonary status initially and at follow-up. PATIENTS AND METHODS: Forty-three nonsmoking patients with systemic sclerosis underwent extensive pulmonary evaluation including pulmonary function tests, chest radiographs, and BAL with analysis of cells, IgG, albumin, immune complexes, and fibronectin. RESULTS: Alveolitis was detected on initial BAL evaluation in 21 patients (49%). Alveolitis was characterized by hypercellular lavage fluid, due to an absolute increase in alveolar macrophages and due to an increase in both the absolute number and percentage of granulocytes (neutrophils and eosinophils). Patients with systemic sclerosis had significantly higher levels of IgG and immune complexes in BAL fluid than did control subjects, and alveolar macrophages from patients with systemic sclerosis released higher amounts of fibronectin in vitro. In serial studies, alveolitis was found to persist. Patients with alveolitis had greater dyspnea than patients without alveolitis (p = 0.02), and they had greater reductions in lung volumes and carbon monoxide diffusing capacity (DLCO) (p = 0.004). Furthermore, patients with persistent alveolitis had significantly greater reductions in pulmonary function over time than patients without alveolitis (forced vital capacity [FVC]: -0.69 L versus -0.05 L, p less than 0.001; DLCO: -2.94 mL/minute/mm Hg versus +0.16 mL/minute/mm Hg, p = 0.03). BAL was used to select patients with alveolitis and at risk of pulmonary deterioration, and treatment was instituted with cyclophosphamide and prednisone, resulting in significant improvement in dyspnea (p less than 0.001) and the rate of change of FVC (p = 0.02) and DLCO (p less than 0.001). CONCLUSION: We conclude that alveolitis occurs frequently in systemic sclerosis and that BAL is useful in identifying such patients who are at risk for a further decline in pulmonary status. Preliminary observations suggest that treatment of patients with active alveolitis may result in improvement in pulmonary status.     

Elevated levels of antimicrobial peptides in bronchoalveolar lavage fluid in patients with chronic eosinophilic pneumonia

BACKGROUND: Chronic eosinophilic pneumonia (CEP) is an idiopathic pulmonary disease. As the lung is in direct communication with the environment, inhaled antigen may activate immune mechanisms in the airway that may participate in the pathogenesis of idiopathic pulmonary diseases. Defensins are antimicrobial peptides that consist of alpha-defensin (HAD) in neutrophils and beta-defensin (HBD) in epithelial cells. Defensins act as innate immunity against pathogens acquired from the environment and as mediators to induce local inflammation. OBJECTIVES: The aim of the present study was to determine whether immune mechanisms in the airway are induced in CEP patients. METHODS: We measured BALF defensin levels in patients with CEP, acute EP (AEP) and drug-induced eosinophilic pneumonia (drug-EP). We also measured BALF levels of IL-5, GM-CSF, eotaxin and RANTES. These substances can recruit eosinophils. RESULTS: BALF HAD levels were higher in patients with CEP than in those with drug-EP and normal controls. HBD-2 was detected in BALF of 10 of 11 CEP patients and in 3 of 5 AEP patients while its level was below detection in drug-EP patients and normal controls. BALF HBD-2 levels correlated with the proportion of lymphocytes in CEP patients. CONCLUSION: The defensin-linked immune system is activated in CEP but not in drug-EP. This suggests that inhaled antigen(s) may be involved in the pathogenesis of CEP.     

Interstitial lung disease in scleroderma. Analysis by bronchoalveolar lavage

Interstitial pulmonary fibrosis is a common feature of scleroderma (systemic sclerosis) which may result in impairment of pulmonary function and may be a major determinant of morbidity and mortality. Clinicopathologic observations suggest that interstitial and alveolar inflammation may appear prior to fibrosis. Using the bronchoalveolar lavage (BAL) technique, we have characterized the nature of the inflammatory process in the lower respiratory tracts of 19 non-smoking scleroderma patients. Eleven of 19 patients (58%) had increased percentages of neutrophils and/or eosinophils in BAL fluid. Five of 10 patients (50%) had elevations of IgG in BAL fluid. The presence of neutrophils was associated with a decreased lung diffusing capacity for carbon monoxide (P less than 0.05) and with more advanced radiographic features of interstitial fibrosis in patients with disease of more than 1 year's duration. This study suggests that scleroderma lung involvement may be characterized by an inflammatory alveolitis and that the presence of such inflammation may relate to the severity of the pulmonary disease.     

Cyclooxygenase- and lipoxygenase-derived eicosanoids in bronchoalveolar lavage fluid from patients with scleroderma lung disease: an imbalance between proinflammatory and antiinflammatory lipid mediators

OBJECTIVE: Eicosanoids play a key role in the regulation of inflammation and fibrosis. Recently we showed that levels of 5-lipoxygenase (5-LOX)-derived proinflammatory/profibrotic leukotrienes are elevated in bronchoalveolar lavage (BAL) fluid from patients with scleroderma lung disease (SLD). The present study was undertaken to investigate whether increased levels of leukotrienes are balanced by the antiinflammatory/antifibrotic cyclooxygenase (COX)- and 15-LOX-derived eicosanoids in the lungs of patients with SLD. METHODS: Levels of 5-LOX-derived leukotriene B(4) (LTB(4)), COX-derived prostaglandin E(2) (PGE(2)), and 15-LOX-derived 15-hydroxyeicosatetraenoic acid (15-HETE) and lipoxin A(4) (LXA(4)) in BAL fluid from systemic sclerosis (SSc) patients with SLD (n = 32) and without SLD (n = 16) and from healthy individuals (n = 12) were measured by enzyme-linked immunosorbent assay. RESULTS: Levels of LTB(4) (mean +/- SEM 248 +/- 29 pg/ml) and PGE(2) (51 +/- 10 pg/ml) in SSc patients with SLD were significantly higher compared with patients without SLD (LTB(4) 119 +/- 35 pg/ml, PGE(2) 17 +/- 3 pg/ml; P < 0.05 for both) and with healthy controls (85 +/- 12 pg/ml and 19 +/- 2 pg/ml, respectively; P < 0.05 for both). Accordingly, the mean +/- SEM PGE(2):LTB(4) ratio was similar in SSc patients with SLD (0.30 +/- 0.05), SSc patients without SLD (0.29 +/- 0.07), and controls (0.31 +/- 0.07). In contrast, levels of 15-HETE and LXA(4) in patients with SLD did not differ significantly from levels in patients without SLD or in controls. The ratio of LXA(4):LTB(4) in SLD patients (0.16 +/- 0.03) was significantly lower (P < 0.05) than that in patients without SLD (0.40 +/- 0.10) or controls (0.34 +/- 0.08). CONCLUSION: Increased production of LTB(4) in the lungs of patients with SLD is not balanced by an up-regulation of 15-LOX-derived antiinflammatory/antifibrotic eicosanoids such as 15-HETE or LXA(4). Targeting the 5-LOX/15-LOX balance may be of practical value in the treatment of SLD.     

Low neutral endopeptidase levels in bronchoalveolar lavage fluid of lung cancer patients

Neutral endopeptidase (NEP) is a cell surface enzyme found in normal human lung and which hydrolyzes small bioactive peptides, some of which act as growth factors for normal and malignant airway epithelial cells. Expression of NEP varies widely in human lung tissue from different individuals. NEP is often expressed at low or undetectable levels in both small-cell and non-small-cell lung cancer, and inhibits the growth of lung cancer cell lines. Variation in the expression of NEP could be a factor in susceptibility to lung cancer. We hypothesized that NEP could be measured in bronchoalveolar lavage fluid (BALF) and that airway levels of NEP would be low in lung cancer patients as compared with normal controls. We measured NEP and total protein in cell-free BALF supernatant, and expressed the respective concentrations as a ratio. NEP levels showed wide variation in BALF of healthy volunteers. Most patients with lung cancer had no NEP detectable in BALF. The mean NEP/total protein ratio was significantly lower in patients with lung cancer (0.87 +/- 0.7 ng NEP/mg protein) than in normal healthy subjects (14.0 +/- 4.3, p < 0.0003). We conclude that NEP levels are highly variable in BALF of normal volunteers, and are low or undetectable in most BALF specimens from patients with lung cancer. Low NEP levels in the airways may be a factor in the pathogenesis of carcinoma of the lung.     

Persistence of abnormal bronchoalveolar lavage findings after cyclophosphamide treatment in scleroderma patients with interstitial lung disease

OBJECTIVE: Bronchoalveolar lavage (BAL) is a procedure for sampling the terminal airspace cell population to diagnose alveolitis, a condition that predicts changes in lung function in scleroderma patients. Cyclophosphamide (CYC) stabilizes the progression of lung disease in some, but not all, patients with active alveolitis. However, it is unknown whether the BAL fluid cell count obtained after CYC treatment of alveolitis predicts long-term lung function outcomes and can therefore be used to assist in therapeutic decision-making. The purpose of this study was to determine whether CYC therapy for active lung disease alters BAL fluid neutrophil and eosinophil counts and whether the persistence of abnormal BAL findings after CYC therapy predicts a decline in lung function in patients with scleroderma and interstitial lung disease (ILD). METHODS: We systematically reviewed the records of scleroderma patients who had active ILD, as evidenced by neutrophilia or eosinophilia on BAL fluid analysis before CYC therapy and on repeat analysis after completion of CYC. Pulmonary function tests (PFTs) were performed before initiation of therapy, at completion of therapy, and during long-term followup (mean +/- SD 3.6 +/- 1.94 years). RESULTS: Of the 25 study patients, in only 6 did the BAL fluid cell counts normalize after CYC therapy. No significant differences were observed between the proportions of patients who had a > or =10% decline in the % predicted DLCO or FVC on the second set of PFTs and had abnormal findings on followup BAL fluid analysis. During long-term followup, patients with persistent alveolitis had a decline in lung function (mean +/- SD change in % predicted FVC -0.6 +/- 10.8 liters and mean +/- SD change in % predicted DLCO -4.7 +/- 21.43 ml/minute/mm Hg), but their lung function did not significantly differ from that in patients whose BAL fluid cell counts had normalized (P = 0.70 and P = 0.62, respectively). CONCLUSION: Persistently abnormal results on BAL fluid analysis following CYC treatment is a common finding and does not predict a subsequent decline in lung function.     

Vitronectin in bronchoalveolar lavage fluid is increased in patients with interstitial lung disease.

Vitronectin, also known as S-protein, is a 75,000-dalton serum glycoprotein that has a variety of functions, including the capacity to interact with the terminal components of the complement cascade, the coagulation system, and cell surfaces. By virtue of its ability to interact with cells, vitronectin is capable of mediating cell-spreading and adhesion and may also influence cell differentiation and cell growth. To investigate the possibility that vitronectin might contribute to the pathogenesis of interstitial lung disease, vitronectin was measured in bronchoalveolar lavage fluid from patients with sarcoidosis, idiopathic pulmonary fibrosis, and, for comparison, normal volunteers. Vitronectin was detected in lavage fluid and serum of all study subjects. Increased lavage fluid concentrations were found in patients with interstitial lung disease when compared with normal subjects (p less than 0.005), and glucocorticoid-treated patients with interstitial lung disease had lower vitronectin levels than did untreated patients. Furthermore, on SDS-PAGE and Western blot analysis lavage fluid vitronectin comigrated with serum vitronectin, suggesting similar molecular size. Thus, vitronectin is a normal constituent of the epithelial lining fluid, and lavage fluid vitronectin is similar to serum vitronectin. The increase of vitronectin concentrations in the epithelial lining fluid of patients with interstitial lung disease suggests that vitronectin may contribute to the pathogenesis of interstitial lung disease.     

支气管分侧灌洗液测定腺苷脱氨酶对肺部疾病的诊断评价

目的　评价肺结核 ,肺癌患者的支气管灌洗液 ( BL F)中腺苷酸脱氨酶 ( adenosinedeaminase,ADA)水平。方法　分别对17例肺癌 ,16例肺结核患者进行了支气管灌洗 ,获取 BL F,测定其中 ADA水平。结果　肺癌患者 BL F中的 ADA为 2 .5 8±2 .68IU/ L,肺结核患者为 7.89± 5 .4 7IU/ L。结论　肺结核患者 BL F中 ADA水平明显高于肺癌患者 ,有显著差异 ( P<0 .0 5 )     

Bronchoalveolar lavage fluid and progression of scleroderma interstitial lung disease

Introduction: So far no clinical or experimental evidences clearly explain how and which systemic sclerosis (SSc) patients will experience a functional and radiological progression of interstitial lung disease (ILD). Objectives: The aim of the study was to investigate whether any bronchoalveolar lavage fluid (BALF) characteristic, compared with clinical, functional and radiological parameters, is associated with the risk of progression of ILD and worse survival in SSc patients. Methods: Lung involvement was evaluated in 110 consecutively examined SSc patients with pulmonary function tests (PFTs) and high‐resolution computed tomography (HRCT); 73 patients with evidence of ILD on HRCT underwent BAL. The progression of ILD was evaluated with PFTs and HRCT after 1‐year follow‐up. A 36‐month survival analysis was assessed. Results: ILD patients with alveolitis had a higher risk to have restrictive lung disease and honeycombing, to experience a worsening in honeycombing score or to develop honeycombing. ILD progression was associated with the evidence of honeycombing on HRCT, with the presence of eosinophils, with an inverted CD4/CD8 ratio and with a higher CD19 percentage count in the BALF or with a positive BALF microbiological culture. The patients with ILD had a worse overall survival. The diffuse disease was the only independent risk factor of overall mortality, and the extent of honeycombing on HRCT was the only independent risk factor of lung disease‐related mortality. Conclusion: Our study suggests the importance of evaluating ILD with HRCT and BAL in order to characterize the risk factors of SSc lung involvement progression. Please cite this paper as: De Santis M, Bosello SL, Peluso G, Pinnelli M, Alivernini S, Zizzo G, Bocci M, Capacci A, La Torre G, Mannocci A, Pagliari G, Varone F, Pistelli R, Danza FM and Ferraccioli G. Bronchoalveolar lavage fluid and progression of scleroderma interstitial lung disease. Clin Respir J 2012; 6; 9–17.     

Immunoglobulin levels in bronchoalveolar lavage fluid of children with chronic chest disease

The concentration and distribution of immunoglobulin isotypes (IgG, IgM, sIgA) and IgG-subclass levels (IgG-1-4) were measured in bronchoalveolar lavage fluid (BALF) in 47 children with chronic chest disease (age range 1.0-9.9 years) and 18 healthy controls (age range 1.0-6.25 years). Of these patients, 19 had nonallergic asthma (Group A), 19 suffered from recurrent pneumonia or chronic bronchitis (Group B), and 9 patients had IgG-2 deficiency (Group C). In all individuals, IgG was the predominant immunoglobulin in the lower respiratory tract, followed by IgA and IgM. In patients of Group A and B, IgG, IgM and IgA levels in BALF were significantly elevated when compared to controls. Assessment of IgG-subclass concentrations in BALF revealed that IgG-1 levels were increased in Group A and B when compared to controls (P < 0.05). Since this difference could not be explained by difference in age, it is possibly due to the inflammatory process at the mucosal level. IgG-2 levels were elevated in all patients except those with IgG-2 deficiency. IgG-2 concentration in the IgG-2 deficent group was lower compared to controls (P < 0.005) and patients in Group A (P < 0.0005) and B (P < 0.005). IgG-3 levels were elevated in asthmatics in group A compared to healthy controls (P < 0.005). IgG-4 concentrations were the same in all study groups. Since IgG-subclasses in percentage of total IgG were similar in BALF and serum, our results do not indicate a local production of any of the IgG-subclasses in the respiratory tract.     

Interleukin 5 and granulocyte-macrophage colony-stimulating factor levels in bronchoalveolar lavage fluid in interstitial lung disease.

The purpose of this study was to evaluate the role of several eosinophil growth factors including interleukin (IL)-5, interleukin (IL)-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the pathogenesis of interstitial lung disease with eosinophilia. IL-5, IL-3 and GM-CSF in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay (ELISA) in patients with eosinophilic pneumonia (EP), bronchiolitis obliterans organizing pneumonia (BOOP), idiopathic pulmonary fibrosis (IPF), sarcoidosis and healthy volunteers. IL-5 in BALF was high only in patients with EP. IL-3 in BALF was undetectable in the majority of patients with these diseases. GM-CSF in BALF was detectable in 30-67% of each group of patients. In patients with BOOP and IPF, the number of eosinophils in BALF was higher in patients with detectable GM-CSF than in patients in whom GM-CSF was below the detection limit. Eosinophil cationic protein (ECP) was detected in all patients with EP and some with BOOP and IPF. There was a significant correlation between ECP levels and percentage or number of eosinophils in BALF. The results suggest the possibility that interleukin 5 in eosinophilic pneumonia, and granulocyte-macrophage colony-stimulating factor in bronchiolitis obliterans organizing pneumonia and idiopathic pulmonary fibrosis may play important roles in eosinophil recruitment in the lung. Activation of eosinophils in the lung is likely to be induced by both interleukin 5 and granulocyte-macrophage colony-stimulating factor.     

A comparison of albumin and urea as reference markers in bronchoalveolar lavage fluid from patients with interstitial lung disease

Lavage fluids were investigated for 67 subjects in 6 groups: 12 with active sarcoidosis, 8 with inactive sarcoidosis, 17 with pigeon breeder's disease, 10 asymptomatic pigeon breeders, 12 with idiopathic pulmonary fibrosis (IPF) and 8 normal subjects. Albumin and urea per ml of bronchoalveolar lavage fluid (BALF) were determined for each subject together with percentage return of fluid (BAL%). Novel assay systems were employed to measure urea and albumin and these were compared with existing analytical techniques. When compared with the control group, we found that urea per ml of BALF was not statistically different for all other groups, except those with pigeon breeder's disease who had significantly raised levels. For albumin, however, three groups had significantly higher levels than the controls, namely those with active sarcoidosis, pigeon breeder's disease and IPF. BAL% return showed no significant differences for any group when compared with the controls. We conclude that since albumin is significantly raised in most patients with interstitial lung disease it does not represent a suitable marker for the quantitation of reactive proteins in BALF. Urea shows much less variability between groups than does albumin, and hence in the absence of a proven alternative represents the most reliable estimate available of epithelial lining fluid dilution during the lavage procedure, providing dwell time is kept to a minimum.