Hypersensitivity Pneumonitis Patients Research Articles

Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP) is a group of immunologically mediated lung diseases caused by the inhalation of environmental agents in susceptible individuals. Most HP patients are non-smokers and have been exposed to organic dusts from vegetable or animal products. Some HP cases are associated with exposures to relatively simple chemical compounds. HP may present as an acute, subacute, or chronic disease and may follow various clinical courses. The type of exposure is thought to be more important in the clinical outcome than the nature of the antigen. A diagnosis of HP is often considered on the basis of clinical history of exposure with resulting respiratory symptoms, but the definitive diagnosis requires a constellation of clinical, radiologic, laboratory, and pathologic findings. The characteristic histologic triad in HP includes bronchiolitis, interstitial lymphocytic infiltration, and granulomas; however, biopsy in HP cases may lack the diagnostic triad and manifest as nonspecific interstitial pneumonia (NSIP). Avoiding exposure to the offending antigen(s) is usually sufficient to resolve symptoms and physiological abnormalities. Pulmonary fibrosis and physiological abnormalities occurring in chronic HP may be irreversible. Steroid therapy is helpful for symptomatic relief, but probably does not affect the long-term prognosis. Type III and type IV hypersensitivity reactions are involved in the pathogenesis; alveolar macrophages and T cells (Th-1 type) play a central role in the immune responses after antigen exposure via their increased interaction and secretion of regulatory mediators.

Hypersensitivity pneumonitis in a metal‐working environment

An outbreak of lung disease among workers in a metal-working plant included 16 biopsy-confirmed cases of hypersensitivity pneumonitis and additional patients with asthma, bronchiolitis and emphysema, usual interstitial pneumonitis, and sarcoidosis. Study design Clinical examination of patients; cross-sectional questionnaire survey of the outbreak plant and two control plant areas, one with and one without MWF exposures, in a separate facility; industrial hygiene survey with laboratory characterization of microbial flora; and immunological investigation. Patients with suspected hypersensitivity pneumonitis underwent a clinical examination including detailed lung function, imaging, and tissue studies. A plant walk-through identified metal-working processes, microbial aerosols, and work practices. Microbial characteristics of the three microbial aerosol-producing processes were characterized. Antibodies to those agents were determined in patient sera. A questionnaire survey was conducted in the case plant and in two areas of a control plant, one with and one without metal-working fluids exposure. Thirty-nine (79.6%) patients described symptoms consistent with work-related lung disease, eight received other diagnoses, and two did not complete their examinations. Sixteen patients had hypersensitivity pneumonitis confirmed on biopsy. Mean decrements in lung forced expiratory volume in 1 s and force vital capacity from before to after work were similar in the 16 biopsy-confirmed cases of hypersensitivity pneumonitis ( - 6.3%; - 7.2%) and the 19 symptomatic patients without biopsies ( - 11.2%, - 10.1%). Symptoms were more common in the case plant than in a non-MWF control plant area. Three sources of water-based aerosols were identified that grew similar microbial flora. Although machining increased airborne bacterial levels, the increase was not related to the concentration of viable bacteria in the sumps. Antibody testing did not identify a specific single organisms. Endotoxin levels were similar in case and MWF control plant. Lung disease in environments with water-based aerosols may be more common than usually recognized. Patients with HP often present with only subtle abnormalities and may be missed if multiple clinical abnormalities are required to document disease.

Granzyme activity in the inflamed lung is not controlled by endogenous serine proteinase inhibitors.

Numerous lung diseases, such as hypersensitivity pneumonitis (HP), are characterized by the presence of activated alveolar CTL and NK cells. Since these cells produce granzymes, granzyme A and B levels in bronchoalveolar lavage (BAL) fluids from 14 normal subjects and 12 patients with HP were measured by ELISA. Median (range) BAL granzyme A and B levels were 4 (0-37) and 0 (0-6) pg/ml in normal subjects. BAL granzyme levels were significantly higher in HP patients, being at 74 (0-1,889) and 10 (0-78) pg/ml for granzymes A and B, respectively. In vitro, neither of the three main serine protease inhibitors of the lung, namely alpha1-antitrypsin, secretory leukocyte protease inhibitor, and elafin, showed any effect on granzyme A or B activity. In addition, granzyme A was shown to be fully active in BAL fluids. Hence, these data show that granzyme activity may be poorly controlled by protease inhibitors in inflamed tissues. Thus, granzymes could contribute to tissue remodeling and inflammation characterizing HP.

Neumonitis por hipersensibilidad en la ciudad de México

To investigate the association between the urban area of origin of patients and the prevalence of hypersensitivity pneumonitis (HP), induced by avian antigens. A case-control study was conducted in 1999 at the National Institute of Respiratory Diseases (NIRD). Cases were 109 consecutive HP patients and controls were 184 patients: 39 with idiopathic pulmonary fibrosis (IPF), 63 with pulmonary tuberculosis (PTB), and 82 with asthma. Mexico City and surrounding counties (SC) were divided into 5 geographical areas: 1) Downtown; 2) North-East (NE); 3) South-East (SE); 4) North-West (NW) and 5) South-West (SW). Statistical analysis consisted of calculation of disease prevalence by urban area; associations were assessed with odds ratios and 95% confidence intervals. Multivariate analysis with multiple logistic regression was performed to adjust for age, gender and socioeconomic level. Eighty HP cases were located in the NE southernmost and SE northernmost areas of Mexico City (48 and 32, respectively) (OR = 3.86; 95% CI 2.17-6.96). Thirty-six controls with asthma came from the SW area, (where NIRD is located) (p < 0.05), and four from SC. Controls with PTB and IPF were scattered throughout the study area. The NE southernmost and SE northernmost areas were associated with HP. The cause of HP may not be geographical; a garbage dump used to be located in this area, suggesting that exposure to organic particles might contribute to the development of HP in susceptible individuals.

Purification and characterization of the allergenic components of shimeji mushroom (Tricholoma conglobatum) spore for shimeji workers' hypersensitivity pneumonitis.

Respiratory symptoms and hypersensitivity pneumonitis (HP) among mushroom workers have been well documented. Inhalation of shimeji mushroom (Tricholoma conglobatum) spore has been assumed to be the cause of HP among indoor shimeji cultivating workers. We isolated and partially characterized the allergenic components of shimeji. The sera from 9 HP patients, 10 asymptomatic shimeji workers and 15 normal individuals were examined for shimeji specific IgG and IgA antibodies by ELISA using crude shimeji extract. Shimeji specific IgG- and IgA-antibodies were higher in sera from HP patients than in sera from control subjects. Crude shimeji spore extract was separated and purified by HPLC followed by SDS-PAGE, and their antigenic activity was studied by immunoblotting with a pool of sera from patients. Sera from all HP patients showed IgG and IgA antibody activities to 21, 16 and 14 kD proteins extracted from shimeji spore. The 21 kD protein contained internal peptide amino acid sequence of Gly-Gly-Thr-Val-Ile-Asn-Leu-Leu-Gly, Gln-Arg-Phe-Glu-Glu and Gln-Gly-Ile-Tyr. These results demonstrate that shimeji spore extract contains multiple proteinous components, which have antigenic activity to react with the sera from HP patients among shimeji workers. These proteins may be the potent sensitizing allergens to cause HP among shimeji cultivating workers.

Expression of C-C chemokines in bronchoalveolar lavage cells from patients with granulomatous lung diseases.

To determine the role of C-C chemokines in the pathogenesis of granulomatous lung diseases, we studied the mRNA levels of C-C chemokines, regulated on activation normal T expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and monocyte chemoattractant protein (MCP)-1 in bronchoalveolar lavage (BAL) cells obtained from patients with sarcoidosis (n = 17), hypersensitivity pneumonitis (HP) (n = 4), and cryptogenic fibrosing alveolitis (CFA) (n = 10) using the reverse transcription-polymerase chain reaction (RT-PCR) technique. The mRNA levels of RANTES, MIP-1alpha, and MIP-1beta in BAL cells were significantly correlated with the lavaged lymphocyte proportion, and a significant inverse correlation was observed between the mRNA level of MIP-1beta and the CD4/CD8 ratio of lavaged lymphocytes. Among the three diseases, the mRNA levels of RANTES and MIP-1alpha were significantly higher in the patients with sarcoidosis or HP compared with those in the patients with CFA. The level of MIP-1beta mRNA was significantly higher in the HP patients compared with that in the patients with sarcoidosis or CFA. No significant differences were observed in the level of MCP-1 mRNA among the three diseases. Thus, RANTES and MIP-1alpha were suggested to be important in the pathogenesis of granulomatous inflammation in sarcoidosis and HP. MIP-1beta might play an important role in the pathogenesis of HP, mediating the recruitment of lymphocytes specific to HP.

Expression of costimulatory molecules on alveolar macrophages in hypersensitivity pneumonitis.

To verify whether alveolar macrophages (AM) of patients with hypersensitivity pneumonitis (HP) increase their antigen-presenting capacity by upregulating the expression of B7 costimulatory molecules (CD80, CD86), and whether a viral infection enhances this expression whereas cigarette smoking abrogates it, we performed bronchoalveolar lavage (BAL) on 18 patients with HP; 10 asymptomatic, virus-exposed subjects (AS); 18 nonsmokers; and 12 smokers. Influenza virus infection of AM from nonsmokers and smokers was induced in vitro. Expression of CD80 and CD86 on AM, and of CD28 and CTLA4 on T cells, was evaluated. The percentage of CD80(+) AM was greater in HP patients (34.6 +/- 7.7) and in AS (23.9 +/- 7.6) than in nonsmokers (6.7 +/- 1.6) or smokers (2.5 +/- 0.3). An increase in CD86(+) cells (62.3 +/- 5.9) was found in HP patients as compared with nonsmokers (24.2 +/- 3.8) and smokers (4.5 +/- 1.0). CD28 and CTLA4 molecules were highly expressed on all T cells. In vitro virus infection upregulated CD80 and CD86 expression in AM of normal nonsmoking subjects but not on those of smokers. These results suggest that: (1) an upregulation of B7 molecule expression is involved in the lymphocytic alveolitis of HP; (2) a viral infection could enhance HP by increasing B7 expression; and (3) the protective effect of cigarette smoking in HP may be due to the low level of expression of costimulatory molecules on AM from smokers, and to their resistance to further upregulation.

Expression of heat shock protein 72 by alveolar macrophages in hypersensitivity pneumonitis.

The current study was done to look at a possible role of heat shock proteins (HSPs) in hypersensitivity pneumonitis (HP). The specific aims were to determine whether there was a difference in the expression of HSP72 in alveolar macrophages (AMs) between mice challenged with HP antigen and saline-treated control mice and between AMs obtained by bronchoalveolar lavage from 18 patients with HP and 11 normal subjects. The expression of HSP72 was studied under basal conditions and under a mild heat shock. HSP72 expression by AMs in response to in vitro stimulation with Saccharopolyspora rectivirgula was lower in AMs of control mice than in those of HP animals. HSP72 was constitutively expressed in AMs of both normal and HP subjects. Densitometric ratios showed that AMs from normal subjects responded to heat shock with a 39 degrees C-to-37 degrees C ratio of 1.72 +/- 0.18 (mean +/- SE), and AMs from HP patients responded with a ratio of 1.16 +/- 0.16 (P = 0.0377). This decreased induction by additional stress of AMs could lead to an altered immunoregulatory activity and account for the inflammation seen in HP.

Surfactant modifies the lymphoproliferative activity of macrophages in hypersensitivity pneumonitis.

Alveolar macrophages (AM) from normal individuals suppress mitogen-induced peripheral blood mononuclear cell (PBMC) proliferation, whereas cells from patients with hypersensitivity pneumonitis (HP) enhance PBMC. Because surfactant components can interfere with AM functions, we tested the effect of Survanta (a modified bovine surfactant) and surfactant fractions isolated from bronchoalveolar lavage of normal subjects and HP patients on AM-induced lymphoproliferation. Surfactant fractions were isolated from bronchoalveolar lavage fluids by differential centrifugation into total aggregates (TA) and large aggregates (LA). Surfactant preparations (200 micrograms/ml) from 10 normal subjects (N) or 12 HP patients or of Survanta were added to AM-PBMC cocultures stimulated with phytohemagglutinin (PHA) at 1:1 and 2:1 ratios. Results, expressed as percent of PHA-induced PBMC proliferation cocultures without surfactant, show that normal surfactant and Survanta decrease mitogen-induced proliferation of cells to a larger extent than surfactant from HP patients. For AM-to-PBMC ratios of 1:1, the results were as follows: N TA 10.58 +/- 2.75% (mean +/- SE), N LA 12.96 +/- 2.78%, HP TA 43.09 +/- 7.81%, HP LA 61.64 +/- 7.77%, and Survanta 16.70 +/- 2.95%. Similar data were obtained in 2:1 cocultures. Because surfactant components interact with AM, alterations of surfactant composition in lymphocytic diseases, mainly in the LA fraction, may account for the lack of suppressive activity in AM of HP patients and the observed alveolitis.

Partial sequences of large subunit ribosomal DNA of a new yeast species, Trichosporon domesticum and related species.

We determined the partial sequences of large subunit rDNA of a new yeast species, Trichosporon domesticum, which was isolated from the house of a summer-type hypersensitivity pneumonitis patient. Phylogenetically, T. domesticum was positioned in the taxonomic group containing T. montevideense and T. brassicae, which indicated an identical serotype. A phylogenetic relationship among all species of the genus Trichosporon which belong to the basidiomycetous yeast is clarified.

A new species, Trichosporon domesticum, isolated from the house of asummer-type hypersensitivity pneumonitis patient in Japan.

A new species, Trichosporon domesticum Sugita, Nishikawa et Shinoda, is proposed for a strain isolated from the house of a summer-type hypersensitivity pneumonitis patient in Kumamoto, Japan. The nuclear DNA of T. domesticum showed intermediate relatedness to that of T. montevideense; however, their genome sizes were significantly different. These findings suggest that they represent separate species. T. domesticum is distinguished from T. montevideense by its inability to assimilate D-arabinose, ribitol, and dulcitol. The type strain of T. domesticum is strain M 9401, which has been deposited in the Japan Collection of Microorganisms as JCM 9580.

Differential Proliferative Characteristics of Alveolar Fibroblasts in Interstitial Lung Diseases: Regulative Role of IL-1 and PGE2

Fibroblasts (Fb) from patients with sarcoidosis (SA) and hypersensitivity pneumonitis (HP) exhibited a lower proliferative capacity compared with Fb obtained from control (CO) and diffuse interstitial fibrosis patients (DIF). Proliferation of Fb from SA or lip patients was suppressed by autologous LPS-stimulated alveolar macrophages (AM) supernatants but not by those from CO patients. Similarly, alveolar macrophages (AM) derived supernatant, obtained from CO, did not suppress the proliferation of SA and HP Fb. AM from SA and HP patients secreted higher amounts of IL-1α and β compared with controls and compared with Fb from SA and HP patients. Steady levels of IL-1α and βmRNA were expressed in unstimulated and stimulated cultures. Fb from SA and HP patients could be stimulated by LPS to secrete significantly higher levels of PGE2 than those detected in supernatants from LPS stimulated Fb of DIF patients. Only the proliferation of Fb from SA and HP patients was sensitive to amounts of IL-1 equivalent to those detected in the lung of these diseases. As SA and HP are two diseases where irreversible deterioration occurs in only 20% of the patients, we hypothesize that mediators in the lung may modulate Fb proliferation. IL-1 of AM origin and PGE2 of Fb origin secreted at high levels, may be candidates for this suppression because it was abrogated by anti IL-1β and indomethacin.

Increased gamma/delta-positive T-cells in blood and bronchoalveolar lavage of patients with sarcoidosis and hypersensitivity pneumonitis

A small population of T-cells does not express the conventional T-cell receptor (TCR), characterized by the alpha and beta polypeptide chains (alpha/beta TCR) but two polypeptides termed gamma and delta (gamma/delta TCR). Changes in gamma/delta TCR expression may be relevant as the cause or consequence of several diseases. Our study was undertaken to determine and compare the distribution of T-cells expressing gamma/delta TCR in blood and bronchoalveolar lavage (BAL) of patients with sarcoidosis, hypersensitivity pneumonitis (HP), idiopathic pulmonary fibrosis (IPF), and of healthy controls. In addition, the association between gamma/delta TCR of blood T-lymphocytes and accessory molecules was analysed. Using direct immunofluorescence with the anti-gamma/delta TCR and anti-CD3 monoclonal antibodies (MoAbs) followed by flow cytometric analysis, the blood of patients with pulmonary sarcoidosis, HP, IPF and of healthy controls was analysed. To reveal the association between gamma/delta TCR of blood T-lymphocytes and the accessory molecules, expression of CD4, CD8 and CD25 were determined. Calculating the percentage and the total number of CD3+ gamma/delta TCR cells in blood, the data indicated a significant increase of gamma/delta T-cells in individuals with pulmonary sarcoidosis and HP, compared to healthy controls and IPF patients. In sarcoidosis patients with elevated CD3+ gamma/delta TCR levels, significantly lower CD4/CD8 ratios were observed. In addition, our data demonstrate a correlation between the decrease of CD4+ cells in blood and the amplified appearance of gamma/delta TCR expression in sarcoidosis patients, but not in HP patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchoalveolar lavage procollagen-III-peptide in recent onset hypersensitivity pneumonitis: correlation with extracellular matrix components

Hypersensitivity pneumonitis (HP) is characterized by the accumulation of inflammatory cells in the lung parenchyma, and may progress to fibrosis. The content of the fibroblast derived collagen metabolite procollagen-III-peptide (PCP-III) in bronchoalveolar lavage (BAL) fluid of HP patients has been found to be increased. Previous studies have shown elevation of the fibroblast adhesion molecules, vitronectin and fibronectin in the BAL fluid of recent onset HP. In view of these observations, it was hypothesized that increases in PCP-III would be associated with increases in vitronectin and fibronectin in the BAL fluid of subjects with untreated recent onset HP. BAL was performed in 14 patients with HP and nine normal controls. The aminoterminal domain of PCP-III was measured by radioimmunoassay, and vitronectin and fibronectin by enzyme-linked immunosorbent assay. Detectable amounts of BAL PCP-III were seen in all HP patients but not in the normal controls (mean +/- SEM 5.1 +/- 1.2 versus < 0.2 ng.ml-1; i.e. below the limit of detection of the PCP-III assay). The BAL fluid concentration of PCP-III correlated well with the amount of vitronectin (r = 0.638) and fibronectin (r = 0.710). Except for PCP-III and mast cells, no significant correlations were found between PCP-III, vitronectin, fibronectin and the cellular parameters. The findings suggest that an increased turnover of collagens and proteoglycans is present in the lower respiratory tract of patients with recent onset HP, possibly reflecting remodelling of the extracellular matrix.

Lowered Responsiveness of Bronchoalveolar Lavage T Lymphocytes in Hypersensitivity Pneumonitis

We previously reported that Trichosporon cutaneum was the major causative antigen of summer-type hypersensitivity pneumonitis (HP) in Japan. In summer-type HP patients, we noticed that the proliferative responses of bronchoalveolar lavage (BAL) lymphocytes to phytohemagglutinin (PHA) and concanavalin A were significantly lower than those of the peripheral blood lymphocytes of the same patients. It was shown in this study that the low response of BAL lymphocytes was due to an intrinsic lowering of the responsiveness of the T cells. Results of the mixed culture experiments, in which the responses to mitogens of BAL and peripheral blood T cells mixed with either alveolar macrophages or blood monocytes were compared, indicated that the decreased proliferative response was due neither to the suppressive effect nor to defects in accessory function of the alveolar macrophages. BAL T cells did not act as suppressor cells when they were added to the culture of peripheral T cells. The decreased proliferative response was not due to the dominance of CD8+ T cells frequently seen in BAL cells of HP patients, because both CD4+ and CD8+ T cells separated from BAL cells of HP patients showed lower responsiveness than those of peripheral blood T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary alveolar macrophages in patients with sarcoidosis and hypersensitivity pneumonitis: characterization by monoclonal antibodies.

Using a panel of monoclonal antibodies (MoAbs), the frequency of cells bearing Class I and Class II major histocompatibility complex (MHC) determinants, transferrin receptor (TR) sites, and interleukin-2 receptors (IL-2R) has been evaluated on pulmonary alveolar macrophages (PAM) recovered from the bronchoalveolar lavage (BAL) fluid of 21 patients with pulmonary sarcoidosis (including 11 cases with active sarcoidosis and 10 cases with inactive disease), 8 patients with hypersensitivity pneumonitis (HP), and 6 normal non-smoking volunteers. When the frequency of Class II DR-positive cells was considered, 64.3% of control PAM expressed HLA-DR products. No statistically significant differences were observed between controls and sarcoid patients, while HP patients showed an enhanced proportion of DR+ PAM with respect to normal PAM (P less than 0.05). On the contrary, the frequency of PAM expressing HLA-DQ molecules was higher in both active sarcoidosis and HP patients with respect to patients with inactive sarcoidosis and normal subjects (P less than 0.001). A statistically significant increase in Class I antigen-positive PAM has been demonstrated in HP patients as compared to controls (P less than 0.05). Active sarcoid patients showed a higher number of PAM-bearing TR sites than controls and other groups of patients considered (P less than 0.001). An increase in the percentage of IL-2R-positive PAM has been demonstrated in active sarcoidosis (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Lung T cells in hypersensitivity pneumonitis: phenotypic and functional analyses.

Cells recovered from bronchoalveolar lavage (BAL) and tissue sections from transbronchial lung biopsies were studied in 16 patients with symptomatic hypersensitivity pneumonitis (HP) and in six subjects with a similar history of exposure but without features of disease by using a series of monoclonal antibodies (MoAb) detecting different lymphocyte subpopulations, including T and T subsets, B lymphocytes, and natural killer (NK) cells. Their functional activities in cytotoxic and suppressor assays and the microenvironment in the lung by using immunohistological techniques were also evaluated. It has been demonstrated that the majority of cells recovered from BAL of HP patients are represented by T8 lymphocytes, with a relevant imbalance of the T4/T8 ratio (p less than 0.001). HNK-1+ cells were markedly increased (p less than 0.001), whereas the frequency of cells bearing other NK-related markers (NK-15, VEP 13, Ab8.28, T10, M1, and Fc gamma R) were not significantly increased with respect to controls. Immunohistological study confirmed that the majority of cells infiltrating lung parenchyma are T8+ lymphocytes. The number of HNK-1+ cells detected on lung biopsies was very low in all cases, even in patients with the highest values on BAL suspensions. The evidence of cells bearing the proliferation-associated markers (Tac and T9 antigens) seems to support the hypothesis of a local proliferation in the lung. In terms of phenotypic analysis, the results observed in the group of asymptomatic individuals are qualitatively superimposable on those observed in the HP group, but the magnitude of the phenomenon is less prominent and therefore the data are not as statistically significant as that produced by the comparison between HP patients and the same controls. Functional analysis of BAL T cells from both HP patients and asymptomatic individuals showed suppressor activity in vitro, as determined by the ability to influence a pokeweed mitogen (PWM)-driven B cell differentiation assay. BAL cells from HP patients were also able to display a definite cytotoxic function in vitro, whereas BAL lymphocytes from asymptomatic subjects did not. Taken together, these data demonstrated that cells responsible for the alveolitis in patients with HP are characterized by the expansion of T cells with the phenotype and functions of both suppressor and/or cytotoxic lymphocytes. This expansion is likely to be related to a local immunologic response to the antigenic stimulus and may provide new insights into the pathogenetic mechanisms of this disease, its pathological pattern, and its management.

Early Neutrophil Alveolitis after Antigen Inhalation in Hypersensitivity Pneumonitis

Bronchoalveolar lavage (BAL) was carried out before and after antigen inhalation in ten hypersensitivity pneumonitis (HP) and five control subjects. Control subjects did not show any significant variation in BAL cells after challenge with diluted pigeon serum. In HP patients, the total number of BAL cells increased from (41.5 +/- 16.8) X 10(4) cells/ml before challenge to (84.0 +/- 28.9) X 10(4) cells/ml after challenge. Of greater interest, the values of polymorphonuclear neutrophils in patients increased from 8.3 +/- 9.7 percent before challenge to 41.2 +/- 24.35 percent, 24 hours after antigen challenge (p - 0.0001). Another BAL, carried out a week later, recovered a persistently high number of cells, (74.67 +/- 33.36) X 10(4) cells/ml. However, the percentage of polymorphonuclear neutrophils and lymphocytes did not differ from the initial pre-challenge BAL. Our study demonstrates an immediate and transient neutrophil alveolitis after antigen inhalation in patients with acute hypersensitivity pneumonitis.