Louis E. Siltzbach Memorial Lecture. Concepts of pathogenesis and lung reactivity in hypersensitivity pneumonitis

It is surprising that forms of hypersensitivity pneumonitis do not occur more frequently, given the variety of biologic dusts and airborne antigens that have been found to cause disease. Exposure is almost universal in some occupations that involve handling animals or feed products, and development of humoral immunity occurs in most; however, overt respiratory illness is relatively infrequent or not easily recognized by the subject. What differs between symptomatic and asymptomatic subjects is not certain, but unique host resistance or susceptibility, as the case may be, appears to be a factor. This may have a genetic basis, but this has not been investigated vigorously. With repeated airborne exposure to appropriate antigens, a humoral and a local respiratory antibody response occur but perhaps with little disease consequence, as most subjects so immunized remain clinically asymptomatic. So far as is known, there is no other route of antigenic exposure except through the respiratory tract, but contact with the antigens could occur on the skin or on mucosal surfaces such as the conjunctiva, or antigens could be ingested by swallowing nasopharyngeal secretions. Except for serum antibodies, however, there is little documentation that other systemic organs are affected, as may occur with sarcoidosis. Of course there is great variability in the age of the subjects and the dosage of antigen to which the subject is exposed, and the frequency and duration of exposure can vary considerably. All of these would seem to be easily tested, however, in an animal model where most of the variables could be independently controlled and varied at will. Even the genetic and aging factors, which are the most difficult parameters to control in humans, could be investigated. Yet, it has been very difficult and perplexing not to have created a more faithful model of hypersensitivity pneumonitis in the laboratory. It is virtually impossible to cause predictable lung disease without the use of an adjuvant that will induce some measure of delayed or cellular hyperreactivity. The acute lung disease caused by antigen-antibody reactions seems too explosive and severe, for its acute disease counterpart of hypersensitivity pneumonitis in humans and the persistence of histologic changes in lung tissue is brief and is usually resolved within 1-2 weeks. A chronic model producing granulomas and fibrosis has been difficult to construct, although the work reported by Fulmer and colleagues is very encouraging.(ABSTRACT TRUNCATED AT 400 WORDS)

Intraluminal fibrosis in interstitial lung disorders

The histopathologic and ultrastructural features of intraluminal organizing and fibrotic changes were studied in open lung biopsies and autopsy specimens from 373 patients with interstitial lung disorders, including hypersensitivity pneumonitis (n = 44), idiopathic pulmonary fibrosis (n = 92), collagen-vascular diseases (n = 20), chronic eosinophilic pneumonia (n = 10), pulmonary histiocytosis X (n-90), pulmonary sarcoidosis (n = 62), pneumoconioses (n = 25), Legionnaire's disease (n = 5), drug- and toxin-induced pneumonitis (n = 4), radiation-induced pneumonitis (n = 2), lymphangioleiomyomatosis (n = 11), and chronic organizing pneumonia of unknown cause (n = 8). Three patterns of intraluminal organization and fibrosis were recognized: 1) intraluminal buds, which partially filled the alveoli, alveolar ducts and/or distal bronchioles; 2) obliterative changes, in which loose connective tissue masses obliterated the lumens of alveoli, alveolar ducts or distal bronchioles, and 3) mural incorporation of previously intraluminal connective tissue masses, which fused with alveolar, alveolar ductal, or bronchiolar structures and frequently became reepithelialized. All three patterns had common morphologic features, suggesting that, regardless of their severity, they resulted from a common pathogenetic mechanism, ie, the migration of activated connective tissue cells, through defects in the epithelial lining and its basement membrane, from the interstitial into the intraluminal compartment. Intraluminal buds were observed most frequently in hypersensitivity pneumonitis, chronic eosinophilic pneumonia, and organizing pneumonia of unknown cause. Mural incorporation and, to a lesser extent, obliterative changes were observed in most interstitial disorders and were very prominent in idiopathic pulmonary fibrosis. Mural incorporation and obliterative changes play an important role in pulmonary remodeling, especially when several adjacent alveoli and/or other air spaces are involved. Under these circumstances, intraluminal organization can mediate the fusion of adjacent alveolar structures by intraluminal connective tissue.

Analysis of bronchoalveolar lavage cells and fluids in patients with hypersensitivity pneumonitis: possible role of chemotactic factors in the pathogenesis of disease

The current study concerns immunological mechanisms involved in the pathogenesis of hypersensitivity pneumonitis (HP) by an analysis of the cells and chemotactic factors (CF) obtained by bronchoalveolar lavage (BAL). Nine patients at an acute stage (HP acute, 8 summer type and 1 pigeon breeder's lung) and 4 patients at a quiescent stage (HP quiescent, 3 summer type and 1 pigeon breeder's lung) were included. The results indicate that: CF for polymorphonuclear cells (PMN) in HP acute were significantly more potent than in HP quiescent; CF for mononuclear cells were not significantly different in the groups; the percentage of lymphocytes in HP acute was significantly greater even though HP quiescent revealed greater percentages of lymphocytes as compared to normal controls; determination of T cell subsets employing OKT antibodies revealed the ratio of OKT8+ cells to OKT4+ cells in HP acute was significantly higher than in HP quiescent, and chemotaxis for PMN was marginally correlated with the percentage of OKT8+ cells at the acute stage of disease.

Bronchoalveolar lavage in extrinsic allergic alveolitis

The precise immunopathological mechanism of extrinsic allergic alveolitis explaining the clinical picture as well as the pathological findings is not known. Bronchoalveolar lavage can be a diagnostic help and a method to unravel the pathophysiology of this disease. In the acute stage of extrinsic allergic alveolitis or within 24 h after antigen exposure an increase in the number of neutrophils is seen. After the acute stage, the number of lymphocytes is even higher than in sarcoidosis. In extrinsic allergic alveolitis as well as in sarcoidosis these lymphocytes are mainly T lymphocytes. However, the distribution of OKT 4 and OKT 8 positive lymphocytes was clearly different in both diseases. In sarcoidosis OKT 4 lymphocytes predominate (OKT 4/8 = 7.8) while in extrinsic allergic alveolitis an increase of both OKT 4 and OKT 8 lymphocytes has been found (OKT 4/8 = 1.5). Whether a type III Arthus reaction or a type IV delayed hypersensitivity with an early component is involved, is discussed.

Pulmonary and immune responses to a Thermoactinomyces vulgaris antigen respiratory sensitization in C57BL/6J mice

Lung histology and immune responses were followed during a six month period of Thermoactinomyces vulgaris antigen respiratory sensitization of C57BL/6J mice. Histologically, the mice developed a picture resembling the subacute stage of human farmer's lung. At the early phase of the sensitization a T-cell response was seen in vitro, characterized by an increased spleen but no peripheral blood lymphocyte reactivity to T-cell mitogens at the same time as increased reactivity to the sensitizing antigen was detected. An increase in the percentage of T-cells in the lavage cell population was also seen. The sensitization was associated with the appearance of both IgG and IgA antibodies in lavage and in serum of which lavage IgA antibodies were found to follow the course of the sensitization most accurately. The increase in antibody titers was not, however, reflected in lavage cytology or in lymphocyte reactivity. The results suggest that different immunological reactions may be predominant at different stages of farmer's lung.

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.

Bronchoalveolar lavage and lung histology. Comparative analysis of inflammatory and immunocompetent cells in patients with sarcoidosis and hypersensitivity pneumonitis

To determine whether bronchoalveolar lavage reflects the histologic aspects of the lung histology in patients with sarcoidosis and hypersensitivity pneumonitis, cells recovered from lavage fluid were compared with tissue sections from transbronchial lung biopsies in 33 patients. The evaluation of cellular types and their topographic distribution in situ was determined by using monoclonal antibodies in combination with immunohistochemical techniques. Cell counts in bronchoalveolar lavage and lung biopsies were significantly correlated both in sarcoidosis and hypersensitivity pneumonitis. In fact, the relative proportions of inflammatory and immunocompetent cells recovered from lavage fluid accurately overlapped those observed in lung tissue sections. However, in patients with more pronounced alveolitis, the frequency of macrophages in tissue sections was higher than that observed in the bronchoalveolar lavage, and the degree of lymphocytes in the lavage was higher than that observed in the corresponding biopsy. Specifically, in these patients the lavage underestimated the amount of macrophages in the lung biopsies and overestimated the number of lymphocytes that were present in the lung parenchyma. This was more evident in patients with hypersensitivity pneumonitis, where the intensity of alveolitis was higher than in sarcoidosis. Our data support the idea that, at least in patients with sarcoidosis and hypersensitivity pneumonitis, bronchoalveolar lavage correctly samples the alveolitis. Discrepancies in patients with very high intensity alveolitis could be due to a more pronounced recirculation of lymphocytes from the parenchyma to the alveolar spaces.

Respiratory disease in adult cattle

This article discusses the nomenclature of respiratory disease, acute respiratory distress syndromes, hypersensitivity diseases, chronic respiratory disease, and the differential diagnosis of respiratory disease.

Regional and systemic immune responses to trinitrophenyl derivatives after intranasal and subcutaneous sensitization of mice

The immune responses and accompanying inflammatory local reactions were analyzed in mice sensitized subcutaneously (SC) or intranasally. Administration of picrylsulfonic acid (PSA) by both routes for two 2- or 1-week periods with a 4-week interval resulted in delayed hypersensitivity responses. Serum antibodies of the IgG and IgE and some of the IgA isotype were found, particularly in SC-sensitized animals. The latter animals also had levels of IgG antibodies in their bronchial fluid. Lymph node cells from mice sensitized for 2-week periods demonstrated high spontaneous proliferation. After culture together with spleen cells, these cells exhibited considerable numbers of mast cells, particularly after stimulation with pokeweed and antigen. The lungs from mice sensitized intranasally revealed increased numbers of mononuclear cells around large vessels and mucous cells in the bronchiolar epithelium, although there were individual differences between the animals. The mast cell numbers in the lungs were only slightly increased compared with numbers in nonimmunized animals subjected to ether anesthesia. Animals injected SC with PSA exhibited increased numbers of mast cells in their lungs compared with control mice. Mice sensitized with trinitrophenylated human serum albumin demonstrated some differences in their immune reactivity compared with animals immunized with PSA. Thus, no obvious delayed hypersensitivity appeared, but the IgG antibody titers were higher, and the IgE antibody titers were lower. The cellular responses assessed histologically demonstrated higher mononuclear cell numbers and lower mast cell numbers compared with those observed in animals sensitized with PSA.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of antigens in lung biopsies by immunoperoxidase staining in extrinsic allergic bronchiolo-alveolitis (EABA)

Open lung biopsy specimens of 14 patients with extrinsic allergic bronchiolo-alveolitis (EABA) were studied by immunoperoxidase staining with avidin-biotin-complex method using nonconjugated antisera to Micropolyspora faeni, Thermoactinomyces vulgaris, Aspergillus fumigatus, and Aspergillus umbrosus. Antigenic intracellular material was found in macrophages and giant cells of granulomas in the lung tissue of 8 patients. This finding supports the hypothesis which suggests that macrophages and T-lymphocytes contribute to the tissue injury in EABA.

Bronchoalveolar lavage in acute drug-hypersensitivity pneumonitis probably caused by phenytoin

We have reported a case of acute hypersensitivity pneumonitis, probably caused by phenytoin, in which the results of bronchoalveolar lavage suggested a predominantly lymphocytic type of alveolitis, comparable to the alveolitis of sarcoidosis or chronic hypersensitivity pneumonitis.

Abnormal bronchoalveolar lavage in asymptomatic dairy farmers. Study of lymphocytes

Bronchoalveolar lavage (BAL) was performed on 24 asymptomatic dairy farmers. Thirteen had serum precipitins to Micropolyspora faeni (MF) antigens (Group 1), and 11 were seronegative control subjects (Group 2). All were nonsmokers and had no history of previous lung disease. Thirteen of 24 subjects (9 in Group 1 and 4 in Group 2) had a high percentage of lymphocytes (greater than or equal to 20%) in their BAL. The T-lymphocyte subpopulations as estimated by OKT3, OKT4, and OKT8 monoclonal antibody reactivity were measured in peripheral blood lymphocytes; OKT3 = 58.5 +/- 15.6% for Group 1, and 58.5 +/- 8.7% for Group 2; OKT4 = 40.6 +/- 10.7% and 39.9 +/- 10.0%; OKT8 = 21.5 +/- 10.6% and 22.4 +/- 8.0%, respectively (p = NS). These lymphocyte characteristics were also similar when subjects with a high percentage of lymphocytes in BAL were compared to those with a normal percentage. Specific (MF-coated) chicken erythrocyte lymphocytotoxicity (Group 1, 45.2 +/- 29.5%, Group 2, 49.2 +/- 23.4%), and nonspecific lymphocytotoxicity (Group 1, 43.9 +/- 28.6%, Group 2, 37.9 +/- 18.0%) were also similar. We conclude that a large number of asymptomatic dairy farmers have an increased percentage of lymphocytes in their BAL ("alveolitis") and that peripheral blood lymphocytes in these subjects have normal subpopulations, as assessed by monoclonal antibodies, and normal lymphocytotoxicity.

The morphogenesis and classification of diffuse interstitial lung diseases: a clinicopathological approach, based on tissue reaction patterns

This account gives a clinicopathological overview and classification of diffuse interstitial lung diseases, emphasising the interstitial pneumonias. The morphogenesis and progression of fibrosing alveolitis are discussed in relation to the normal cellular and extracellular components of the pulmonary interstitium, with the alveolar macrophage playing a pivotal role. So-called desquamative interstitial pneumonia is considered to represent an early steroid-responsive cellular exudative phase of fibrosing alveolitis, most of the intra-alveolar cells being macrophages rather than type II pneumocytes. The distinction between fibrosing alveolitis and diffuse alveolar damage, and their possible pathogenetic relationships to each other, are also discussed. Throughout this presentation it is stressed that inflammatory interstitial disorders such as the "desquamative" alveolopathies constitute stereotyped patterns of tissue reaction to a variety of injurious agents, which should always be taken into account in reaching a definitive clinicopathological diagnosis, especially in fibreoptic biopsies where histomorphological discriminants may not be present because of the small amount of tissue sampled.

Animal studies of potential chronic lung disease of workers in swine confinement buildings

The pathologic changes in laboratory animals housed in a swine confinement building were studied to predict potential chronic health effects on persons working in these buildings. Rabbits and guinea pigs were maintained for 12 months either in a confined nursery-grower unit (test animals) or in conventional laboratory animal housing (controls). Necropsies and histopathologic examinations were performed on animals that died prematurely or were killed at termination of the study. Blood serum from the animals was examined for antibodies to extracts from swine confinement house dust. The confinement atmosphere was monitored for environmental pollutants. Concentrations of gases and dust in the air of the confinement building were comparable to those found in a typical swine confinement building. Pulmonic lesions seen in the test rabbits and guinea pigs included diffuse interstitial histiocytic pneumonia. Tracheal and nasal turbinate lesions included epithelial hyperplasia and metaplasia, with submucosal infiltration of plasma cells and heterophils. Blood from the test animals contained serum precipitins to dust extract from confinement houses. The presence of precipitins combined with the microscopic appearance of the lungs indicated that an immunologic process, such as hypersensitivity pneumonitis, may be used to explain the basis of the observed lung lesions. The tracheal and turbinate lesions are best explained as a reaction to a chronic low-grade irritation.

Experimental allergic alveolitis in mice induced by Thermoactinomyces vulgaris

A model of allergic alveolitis was developed in inbred mice. Antigen suspension prepared from Thermoactinomyces vulgaris was applicated intranasally in C3H/He mice. Lung histology, serum IgG and IgA antibodies and serum lysozyme were followed during the course of sensitization. The lung histology showed an increased number of intra-alveolar macrophages and leucocytes in sensitized mice. Interstitial peribronchiolar and perivascular infiltration of mononuclear inflammatory cells and a few granulomas were also detected. An increase in the prevalence as well as titers of IgG and IgA antibodies was recorded during sensitization. An elevation in serum lysozyme level was also observed in sensitized mice. The lung histology of control animals was essentially normal and no increase in antibody titers or lysozyme levels was detected. Intranasal application of antigen prepared from Thermoactinomyces vulgaris seems to produce in mice allergic alveolitis resembling human farmer's lung.

[Bird-breeder's lung. Apropos of a fatal case. Immunohistochemical and anatomo-pathological study]

The authors report the case of a female bird breeder who presented with severe pneumopathy from which she died within two weeks. An autopsy was performed. The case is compared with others taken from the literature and the danger of a severe outcome under certain circumstances is emphasized. The authors advocate recourse to immunohistochemical detection of specific markers.

Clinical episodes of granulomatous pneumonitis. Repetition during four consecutive summers

From summer to mid-autumn for four consecutive years (1974 to 1977), a 50-year-old woman barber experienced cough and exertional dyspnea with sputum production. Rales were audible at the posterior lung bases bilaterally. Her chest x-ray film showed diffuse nodular shadows, and pulmonary function studies revealed markedly decreased DCO. Open chest lung biopsy was performed and granulomatous lesions with multinucleated giant cells without central necrosis were observed. Having experienced multiple episodes for four years, she ceased to show symptoms after demolishing and reorganizing her house. This case is thought to represent the typical summer-type hypersensitivity pneumonitis, which we have subsequently found to be the most prevalent form of hypersensitivity pneumonitis in Japan.

A national survey of bird fanciers' lung: including its possible association with jejunal villous atrophy. (A report to the Research Committee of the British Thoracic Society)

In 143 British patients with bird fanciers' lung (BFL), jejunal biopsy was requested in 25 because symptoms and investigations suggested malabsorption. Fourteen biopsies were performed; jejunal villous atrophy was found in five and increased lymphocytes in jejunal mucosa in two others. Budgerigars and pigeons were the birds most frequently implicated in causing respiratory symptoms. Fever was recorded more often in pigeon fanciers. Twenty-one of 47 patients with budgerigar fanciers' lung were females aged over 65, whereas 29 of 47 patients with pigeon fanciers' lung were males aged under 45 years. Of all patients with BFL, 61% were life-long non-smokers and only 15% smokers, compared with the national average of 40% smokers. Bilateral generalized small radiographic opacities and a restrictive ventilatory defect characterized the disorder. These tended to improve after avian withdrawal only in patients under 45 years of age whose symptoms had been present for less than 2 years. Avian species was not related to the severity of the disorder or to subsequent recovery. Serum precipitins were inconsistent and of no prognostic value.

Pulmonary response to repeated exposure to Micropolyspora faeni

Most human exposure to agents that cause hypersensitivity pneumonitis (HP) result in transient episodes of HP that resolve quickly. We repeatedly injected Micropolyspora faeni, which is responsible for farmer's lung disease, into rabbits in an attempt to elucidate mechanisms for this phenomenom (i.e., resolution of abnormalities). The character and the extent of lung disease, the amount of anti-M. faeni serum antibody, and skin reactivity to M. faeni were evaluated after 3 sensitizing and 2, 4, or 8 challenge injections. We also determined the fate of 125I labeled M. faeni injected intratracheally into both normal and previously exposed rabbits. Increased numbers of lymphocytes, macrophages, and few polymorphonuclear leukocytes were present in interstitial and intraalveolar regions and bronchial walls. Interstitial fibrosis was not observed. The extent of cellular abnormalities was maximal after 2 challenges and regressed thereafter, despite continuing intratracheal injections. Serum anti-M. faeni antibody peaked after 4 intratracheal challenges. Anti-M. faeni antibody level at the time of death appeared to be proportional to the extent of inflammatory reaction within the lung. Previous exposure of rabbits to M. faeni was associated with more rapid appearance of 125I in blood in the first 2 h after intratracheal injection of 125I M. faeni. However, 24 h after injection, there was less 125I in the lungs and more in the urine of immunized rabbits than in normal rabbits. Repeated intratracheal injections of M. faeni into rabbits produces transient interstitial, intraalveolar, and peribronchial inflammatory infiltration that regresses without fibrosis despite continued antigenic challenge. Immunization appears to markedly decrease pulmonary exposure to antigen that results from an intratracheal injection of M. faeni.

Hypersensitivity pneumonitis--pathology and pathogenesis

Early reports of hypersensitivity pneumonitis postulated that the disease was infectious or resulted from the toxic properties of the inhaled organic dusts. The finding of precipitating antibodies to moldy hay in farmers afflicted with farmer's lung suggested a role for antibody in pathogenesis, and a type III (antigen-antibody complex-mediated or Arthus) hypersensitivity reaction based on the classification of allergic reactions by Gell and Coombs was postulated. Subsequent studies have indicated the importance of cell-mediated (delayed) hypersensitivity (type IV). It must be recognized that hypersensitivity mechanisms are quite complicated and that the classification of Gell and Coombs is an oversimplification; interreacting humoral and cellular responses are typical of most hypersensitivity reactions of whatever classic type as originally defined. The prime importance of T-cell- and macrophage-mediated inflammation in HP, however, is indicated by histopathology, animal models, and in vitro correlates in humans. Major difficulties in defining completely the exact effector mechanisms involved in the pathogenesis of HP include the absence of a reliable in vitro correlate of antigen-specific effector T cells (the so called TDH cell) and the overwhelming versatility of the macrophage. There is no direct evidence to support contributions by precipitins, complement, or genetic host factors in the pathogenesis of hypersensitivity pneumonitis, nor are there studies as yet of cellular cytotoxicity contributions. Cellular and antibody interactions may lead to immunosuppressive processes modulating inflammatory responses and preventing disease despite immunogenesis. Animal models are helpful in dissecting mechanisms and defining effector functions. The eventual goal in studies of pathogenesis is to provide better tools for definitive diagnosis and methods of disease prevention, modulation, and cure.

Extrinsic allergic bronchiolo-alveolitis: serology and biopsy findings

Because the diagnosis of extrinsic allergic bronchiolo-alveolitis is usually on a clinical and serologic basis, recent histopathologic descriptions of the syndrome are rare. As the etiology may vary in different countries, so perhaps may the histopathology? Clinical and serological examination was combined with histopathology of open lung biopsy from 14 northern Finnish patients. All of them, after exposure to mouldy dust, had a typical clinical syndrome with cough and/or dyspnoea, some radiographic changes, and a reduced VC and/or DCO. Precipitating antibodies were demonstrated in 11 patients. Histopathologically, oedema, macrophages and granulomas were found in all patients, as were lymphocytic and plasmocytic infiltrates. Inflammatory changes were alveolar, interstitial and bronchiolar, including bronchiolar granulomas in all but one case. None of the patients had severe fibrosis or emphysema. There were no examples of clear-cut acute or chronic stages as described in previous studies. Instead, most of our specimens represented an "intermediate" stage, indicating differences in exposure or susceptibility of the population compared with other countries.

Characteristics of the cellular composition, especially the lymphocyte sub-populations of bronchoalveolar lavage fluid from patients with summer-type hypersensitivity pneumonitis

The pathogenesis of summer-type hypersensitivity pneumonitis, which often occurs in Japan, was examined by analysing the cell profile, especially the lymphocyte sub-populations, of bronchoalveolar lavage fluid from these patients: twenty-two normal volunteers and fourteen patients with localized lung cancer as controls. Lymphocyte sub-populations were determined by the micro-testplate method. In the bronchial fluid of the summer hypersensitivity groups, the total cell number was much higher (five to ten times) than in the control groups, and the percentage of lymphocytes reached 84.2 +/- 5.1% (mean +/- s.e. mean); the percentage of T lymphocytes was significantly increased (95.6 +/- 1.0%), but that of B lymphocytes (3.2 +/- 0.6%) was similar to that of the control groups, though the absolute numbers of B and T lymphocytes were higher than in the control groups. In the peripheral blood of the summer hypersensitivity group, the percentage of B lymphocytes was significantly higher than that found in the normal volunteers, but that of T lymphocytes was not increased. Cellular changes in bronchial fluid were more evident than changes seen by X-ray examination and are considered to be a good parameter of the severity of hypersensitivity pneumonitis. It is considered that cell-mediated immunity as well as the Arthus reaction may be intimately related to the pathogenesis of summer-type hypersensitivity pneumonitis.

Hypersensitivity pneumonitis in man. Light- and electron-microscopic studies of 18 lung biopsies

Light- and electron-microscopic changes produced by hypersensitivity pneumonitis were analyzed in open lung biopsies taken from 18 patients with chronic forms of the disease. The main changes observed were: alveolitis (both luminal and mural), granulomas, intraalveolar buds, and interstitial fibrosis. The cells infiltrating the alveolar walls were mainly lymphocytes. Occasionally these lymphocytes presented irregularities in the contours of the nuclear membranes and resembled Sézary cells. In one patient, a few lymphocytes were found that resembled "hand-mirror" cells. Intraalveolar macrophages often had a foamy appearance. Granulomas, present in two-thirds of the patients, differed in several respects from those in sarcoidosis: they were smaller, more loosely arranged, and poorly limited; they had a higher content of lymphocytes; and they were located more frequently in alveolar tissue than in the vicinity of bronchioles and vessels. Intraalveolar buds, also present in about two thirds of the patients, were composed mainly of fibroblasts, myofibroblasts, and macrophages in a loose connective tissue that was rich in proteoglycan material. Capillaries and epithelial cells were rarely seen in buds. Alveolar buds appear to develop by a process of disruption of the epithelial lining layer, due to alveolitis, followed by intraalveolar exudation and by subsequent intraalveolar migration of connective tissue cells interacting with macrophages. Severe fibrotic and alveolar epithelial changes were observed in four patients; milder changes were frequent in most other patients. It is concluded that hypersensitivity pneumonitis usually has distinctive morphologic features; these may help to distinguish the resultant pulmonary fibrosis from that due to other causes.

Carrier requirement for development of acute experimental hypersensitivity pneumonitis in the rabbit

Fluorescein isothiocyanate (FITC) conjugated to protein carriers was used to explore carrier dependence in an established rabbit model of acute hypersensitivity pneumonitis (HSP). Rabbits were immunized via toepads with either FITC-ovalbumin (OA) or FITC-human gamma-globulin (HGG) in complete Freund's adjuvant, and were aerosol challenged with homologous or heterologous conjugates 30 days later. Only those rabbits challenged with the homologous carrier developed acute HSP, despite the presence of comparable levels of anti-FITC antibodies in the sera of all groups. These findings indicate a strict carrier dependence in the pathogenesis of HSP in this model and provide further evidence that the mechanism of inflammation depends upon a cellular immune response.

Bronchoalveolar lavage and transbronchial lung biopsy in sarcoidosis and extrinsic allergic alveolitis

Bronchoalveolar lavage (BAL) and transbronchial lung biopsy (TBLB) in the same endoscopic session were performed in 44 patients: 20 were affected by active sarcoidosis (AS), 15 by inactive sarcoidosis (IS) and nine by extrinsic allergic alveolitis (EAA). Compared with 12 healthy controls, in EAA and AS patients the total number of cells and the percentage of lymphocytes were increased both in smokers and non-smokers. TBLB showed sarcoid granulomata in 15 AS and six IS patients, interstitial fibrosis in four AS and seven IS patients, and normal lung tissue in two IS patients. In EAA, TBLB revealed granulomata or mononuclear infiltrates in four patients and fibrosis in a further four. Regarding the correlation between TBLB and BAL, sarcoid granulomata were more frequently found in patients with AS, as reflected by the increased number of lymphocytes in BAL. The procedure produced no significant complications.

The local and systemic IgA and IgG antibody responses of rabbits to a soluble inhaled antigen: measurement of responses in a model of acute hypersensitivity pneumonitis

We evaluated local and systemic humoral responses to inhalational challenges with ovalbumin (OA) by measuring IgA and IgG isotypic antibodies to OA in serum and bronchoalveolar wash fluids (BAW), and by quantitating cells containing IgA, IgG, and anti-OA in lung, lymph nodes, spleen, and gut. Rabbit models of acute hypersensitivity pneumonitis and chronically-challenged "desensitized" animals were studied along with appropriate control animals. Systemic (via a toe pad) immunization or acute aerosol challenge with OA resulted in only trace amounts of IgG anti-OA antibodies in BAW and no apparent anti-OA-containing cells in the lung itself. Acute aerosol challenge of systemically immunized rabbits caused alveolitis, increased IgG anti-OA-containing cells in mediastinal and popliteal lymph nodes, and increased IgG anti-OA in BAW attributable to transudation from serum. Thrice-weekly inhalational challenge with aerosolized OA resulted in waning alveolitis, elevated concentrations of IgA and IgG anti-OA in BAW and serum, and increased concentrations of IgG and IgA anti-OA cells in the lung, but not in other tissues, including the gut. We conclude that these experiments have implicated IgG as well as IgA antibodies in local humoral responses to inhaled antigen, have not substantiated the notion of a common mucosal immune system involving lung and gut, have failed to demonstrate humoral tolerogenesis after inhalation of antigen, and have shown an effect of systemic priming on subsequent pulmonary immune responses in the models examined.