Thorax: first published as 10.1136/thx.40.5.321 on 1 May 1985. Downloaded from Thorax 1985;40:321-327

Editorial The alveolar macrophage

The macrophage The lung is unique in providing access to large numbers of macrophages by use of the technique of CLASSIFICATION bronchoalveolar lavage. In no other organ can a Almost one hundred years ago Metchnikoff large yield of cells be obtained by an atraumatic identified a large cell capable of phagocytosis which technique. This ideal means of studying the mac- he called the macrophage.' For many years its role rophage and related non-lymphoid cells has pro- was interpreted as that of a scavenger of debris and duced important information about the immunolog- microbes; but in recent years attention has focused ical mechanisms and biochemical features of the on the origin, structure, and function of the mac- macrophage in lung disease. rophage. It has become clear that the macrophage and closely related non-lymphoid mononuclear cells ORIGIN OF THE MACROPHAGE participate in a wider range of activities, which are Although the origin of the pulmonary macrophage central to the continued well being of the host. has been the subject of keen debate in recent years, Originally classified as belonging to the rather there now seems little doubt that the cells are nebulous "reticuloendothelial system," the mac- derived from bone marrow. Animal studies4 and, rophage has come to be regarded as part of the more recently, studies on patients who have mononuclear phagocyte system.2 All the cells received bone marrow transplants5 have confirmed included in this system, from the bone marrow stem the origin of the cells. A small percentage of cells cell to the tissue macrophage, are classified as are, however, capable of further division within the belonging to a single system based on similarities of interstitium and alveolus, once the target organ has cellular morphology and function. Even this scheme been reached.4 The average life span for an alveolar requires some modification with the identification of macrophage in man has been estimated to be of the the veiled cell, interdigitating cell, and the order of 81 days, but a population of more long lived http://thorax.bmj.com/ Langerhans cell, all of which are derived from bone cells seem likely to be sited within the interstitium. marrow like the macrophage and all of which have important individual roles in the immune response as antigen presenting cells.3 They are not mac- TERMINOLOGY rophages, however, and will not be discussed in As blood monocytes migrate into tissue there is a detail. With light microscopy alone it may be process of structural and functional evolution. The difficult to distinguish these other cells from monocyte may become a resident macrophage or, at mac- sites of inflammation, an exudate (inflammatory)

rophages and it is impossible to distinguish between on October 1, 2021 by guest. Protected copyright. different forms of macrophages (exudate, resident, macrophage. These two types of tissue macrophage and activated). Preoccupation with light microscopic may be distinguished by ultrastructural analysis and appearances led to the persistence of an oversim- by markers such as peroxidase content (greater in plified view of the macrophage and a general un- exudate macrophages) and 3 galactosidase content awareness of the different cell types that are present. (higher in resident macrophages). On the other This in turn precluded an understanding of the dif- hand, the term activation refers to a series of fering functional roles fulfilled by the cells in various changes within the macrophage by which it acquires chronic inflammatory states. Only by ultrastructural a new or additional functional capacity in response analysis using the electron microscope, the applica- to stimulation by factors in the local milieu. The tion of sophisticated cell surface receptor recogni- nature of the stimulating agents is diverse and acti- tion markers, and the identification of intracellular vation takes forms that vary with the nature of the enzymes can the various cell types (macrophage, stimulus. The term has been much abused over interdigitating cell, etc) be differentiated and more recent years and it has often been assumed that acti- informed assessment of their function made. vation for one particular function results in activa- tion for all possible macrophage functions. This is not the case and the term must now be used with Address for reprint requests: Dr RM du Bois, Royal Free Hospital, reference to the stimulus inducing the change and London NW3 2QG. the functional capacity of the cell after the change. 321 Thorax: first published as 10.1136/thx.40.5.321 on 1 May 1985. Downloaded from

322 For example, a two hour pulse of the lymphokine and monokines; while many receptors and surface macrophage activating factor induces enhanced antigens such as Fc, complement, and histocompati- expression of Ia antigen on the surface of the mac- bility antigens have been identified. These attributes rophage, making it capable of antigen presentation. endow macrophage like cells with enormous func- On the other hand, continual exposure to mac- tional capacity, which is reflected by the part these rophage activating factor activates the cell to pro- cells play in a wide range of biological activities. duce hydrogen peroxide, which is necessary for bac- Much of our understanding of the cells of the terial killing and antibody dependent cytolysis. This mononuclear phagocyte system comes from animal diversity of response is important not only for studies, particularly those on the mouse and the understanding pathogenic mechanisms in which rabbit, and some caution is necessary in applying macrophages take part but also for the future information obtained from animal macrophages to development of therapeutic tools by which these man. It is not proved that functional capacity is iden- changes might be modified. tical in macrophages obtained from different ani- Certain structural attributes of the macrophage mals or even in macrophages obtained from differ- are associated with a particular function. For exam- ent sites within the same animal. ple, the expression of DR antigen on the surface of the macrophage is necessary for antigen presenta- Methods ofstudying macrophage function tion to T lymphocytes. Thus recognition of struc- The study of macrophage function in vitro requires a tural differences in the cell in tissue allows reasoned source of free macrophages, since cells obtained by interpretation of functional potential. tissue extraction are difficult to process and the pro- In view of the absolute number of non-lymphoid cessing may affect the subsequent behaviour of the mononuclear cells of monocyte lineage present in cells in culture. tissue and the variety of functions that these cells The mouse peritoneal cavity was one of the ear- may perform in response to the varying nature of the liest sources of macrophages and cells could be stimulation (see below), the word macrophage as it retrieved by peritoneal lavage. Cells were obtained is currently used is clearly an umbrella term for a in varying states of activation or stimulation by vast, heterogeneous population of cells. applying various intravenous or intraperitoneal inflammatory stimuli in vivo before lavage. The FUNCTION OF MACROPHAGES effects of these stimuli on macrophage morphology

One of the earliest series of experiments on mac- in culture, secretion of a range of lysosomal and http://thorax.bmj.com/ rophage function was undertaken by Mackaness in other enzymes, phagocytic capacity, and microbici- the 1960s.6 He described the part played by the dal enhancement were then observed. In addition, macrophage in cellular immunity to intracellular different agents were applied in vitro to cultures of parasites. Macrophages obtained from animals macrophages which had received no in vivo stimula- infected with intracellular parasites are morphologi- tion, and the changes in the same morphological and cally different from normal cells. They contain an functional characteristics were noted. Research of enlarged Golgi apparatus, more free ribosomes, and this kind has produced information which has an elaborate endoplasmic reticulum. The cells advanced understanding of the cell biology of spread more avidly in vitro, have an enhanced chronic inflammation and provided experimental on October 1, 2021 by guest. Protected copyright. phagocytic ability and increased content of methods that could be applied to human mac- lysosomal enzymes, and become effective microbi- rophages. cidal cells. More recently, the capacity for the mac- Studies of human alveolar macrophages may be rophage to destroy cells as well as microbes has divided into two main types. Firstly, macrophages become established (for review see 7), and in the from patients with known diseases can be cultured last decade the versatility of the macrophage in and the spontaneous secretion of compounds into terms of secretory products, interactions with other cell culture media may be assessed (for example, immune and inflammatory cells, and the expression neutrophil chemotactic factors). The second of cell surface receptors has been recognised. The approach has been to obtain macrophages from the macrophage is known to be capable of secreting lungs of normal volunteers and to apply varied more than 50 secretory products and the expression stimuli to cultures of these cells in vitro. An example of more than 30 surface receptors has been of this sort of study is the application of immune described, although an individual cell may not pos- complexes to cell cultures and the observation that sess all of these capabilities. The secretory products this stimulus induces the macrophage to secrete include hydrolytic enzymes, proteolytic enzymes, neutrophil chemotactic factor. With these two types antiproteases, complement factors, arachidonic acid of study several important macrophage secretory metabolites, reactive oxygen species, fibronectin, products have been identified. Furthermore, cell Thorax: first published as 10.1136/thx.40.5.321 on 1 May 1985. Downloaded from 323 surface receptors can be identified immediately after superoxide may be linked to increased hexose lavage and changes in receptor expression moni- monophosphate shunt activity as NADP is necessary tored during culture in the presence or absence of for the oxidation of glucose-6-phosphate to stimuli (for example, Fc component of immuno- 6-phosphogluconate, which is an early reaction in globulin, C3b component of complement). the hexose monophosphate shunt pathway. Hyd- Other macrophage functions which can be studied rogen peroxide may be produced by further reduc- with a lavage population are phagocytosis of bac- tion of superoxide and this then reacts with another teria or particulate material (such as latex particles molecule of superoxide to generate hydroxyl radical. or zymosan), bactericidal capacity, and-perhaps of In addition, the interaction of hydrogen peroxide most interest-interactions with other inflammatory with halide anions generates hypohalous acids. cells (for example, the effect of the macrophage on These oxygen derived reagents are necessary for lymphocyte transformation in response to an anti- microbicidal and possibly antibody mediated gen stimulus: the ratio of macrophages to lympho- tumour cell lysis, but they are also potent agents that cytes has been shown to be a crucial factor in deter- may cause peroxidation of cell membrane lipid mining whether the macrophage effect is enhance- components and therefore cellular damage. ment or suppression-as macrophage numbers Inhibitors of oxygen radicals are necessary to main- increase, a suppressor response develops8). tain tissue homeostasis. Superoxide dismutase cata- lyses the conversion of superoxide to hydrogen Antimicrobial function peroxide, and this is degraded by catalase and also The antimicrobial function of the macrophage glutathione peroxidase. These enzymes are present requires, firstly, the recognition of organisms by the within alveolar macrophages. There are other non- macrophage and, secondly, their subsequent des- specific oxygen radical scavengers, such as ascorbic truction. The exact mechanisms whereby mac- acid; but the relative importance in vivo of these rophages can identify organisms are not clearly scavengers is unknown. (For reviews see 7 and 9.) understood, but the presence on the surface of the It must be emphasised that the mechanism macrophage of receptors for the Fc component of whereby a macrophage is activated to kill micro IgG and the C3b component of complement is organisms probably differs for different organisms. almost certainly required for the phagocytosis of The activation for the killing of rickettsiae, for opsonised bacteria. Other receptors, such as those example, requires an initial priming by lymphokines for the mannose receptor and non-specific surface

followed by a second signal from, for example, http://thorax.bmj.com/ receptor recognition systems, probably also play a endotoxin.'° The identification of the variety of fac- part. After becoming attached to the surface bac- tors that can prime or trigger killing is currently the teria are phagocytosed by a complex process which subject of active research. Irrespective of the exact includes the invagination of part of the surface mechanisms of microbe killing, fusion of lysosomes membrane to form a phagosome within the cyto- with phagosomes allows the phagocytosed material plasm of the cell. The production of a phagosome to be degraded by lysosomal enzymes. requires an intricate arrangement of microfilaments, including actin and myosin.9 Antitumour activity

The fate of the ingested organism varies-the The macrophage has the capacity to become on October 1, 2021 by guest. Protected copyright. result may be complete destruction or its persistence cytotoxic to tumour cells in two ways. The first is a as an intracellular parasite. Associated with direct effect of cell to cell contact and the second is phagocytosis is the "respiratory burst," which gen- antibody dependent. The direct mechanism of mac- erates reactive oxygen species such as superoxide, rophage induced tumour cytotoxicity involves the hydrogen peroxide, singlet oxygen, and hydroxyl binding of macrophage to tumour cells and then the radicle.7 The respiratory burst is an increase in cell secretion of a protease, cytolytic protease, capable metabolism that follows phagocytosis, consisting of of lysing the tumour cell." In the process whereby an increased oxygen consumption by the cell and the macrophage becomes activated to secrete cytoly- increased glucose metabolism via the hexose mono- tic protease it is primed with a lymphokine (cur- phosphate shunt pathway. Associated with these rently thought to be y interferon), and a second changes is an increase in the production of super- signal (for example, traces of endotoxin) stimulates oxide anions by the phagocyte. Though its exact enzyme release. In antibody dependent tumour kil- biochemical nature is not known, the generation of ling the tumour cells must first be coated by anti- superoxide ,is probably due to an oxidase system body, as this form of tumour cell lysis depends on associated with the cell membrane. As this oxidase recognition by the macrophage of the Fc fragment of system oxidises, preferentially, NADPH to NADP it immunoglobulin. The final step in tumour lysis by has been called NADPH oxidase. The generation of this mechanism is unclear but may depend on the Thorax: first published as 10.1136/thx.40.5.321 on 1 May 1985. Downloaded from 324 formation and release of hydrogen peroxidase.'2 however, been no studies that have been capable of There have been few studies of the functional relating expression of the DR antigen to function, capacity of human alveolar macrophages to kill and the functional significance of this expression is tumour cells, although Swinburne et al'3 have shown still unclear. that, at a macrophage to target cell ratio of 20:1, The use of monoclonal antibodies to other surface human alveolar macrophages were capable of 100% antigens on the macrophage will allow phenotyping cytotoxicity for a human lung adenocarcinoma cell of the macrophage subsets, both in tissue20 and in line. Vose'4 isolated macrophages from human lung free cell suspension (DA Campbell and colleagues, tumours and found that they could express cytolytic unpublished findings). Such techniques will not only activity against fresh tumour target. Lemarie et al,'5 provide differentiation of distinct subgroups but measuring alveolar macrophage chemotaxis in sam- enable these subgroups to be separated so that ples from a large number of individuals with various proper functional studies can be performed. In a forms of lung disease, found that chemotaxis was series of experiments on open lung biopsy tissue significantly less in samples obtained by lavage from from patients with fibrosing alveolitis, Campbell the neighbourhood of a tumour than in samples et a2' have demonstrated the presence of several obtained from patients with other lung disease. It is phenotypically distinct macrophages within the tis- not clear from this study whether the macrophage sue. The interstitial macrophages almost universally defect was intrinsic or whether a tumour factor express the DR antigen, whereas within lymphoid could have influenced macrophage chemotaxis. Cur- aggregates the presence of non-lymphoid mononuc- rent evidence from human studies suggests therefore lear cells bearing distinct antigens typical of dendri- that macrophages can kill tumour cells but that a tic reticulum cells in association with T helper lym- macrophage defect exists in patients with lung phocytes and B cells has shown that true germinal tumours. The exact nature of this defect, or whether centres have developed within the lung of patients it is primary or secondary to tumour factors, is not with this disorder. High levels of immunoglobulins, clear. Whether or not the macrophage can be circulating immune complexes, antinuclear factor, restored to full tumoricidal capacity is not known, and rheumatoid factor have been found not only in but with increasing knowledge and understanding of the blood but also in lavage fluid from patients with the stages concerned in macrophage activation for this disorder. This raises the intriguing possibility tumour cytolysis it may eventually become possible that, in addition to being the target organ, the lung

to prime and trigger cytotoxicity in vivo. may be the origin of these immunoglobulins and http://thorax.bmj.com/ complexes. Role of the macrophage in immunity The generation of an immune response to protein Human alveolar macrophages antigen requires the activation of helper T cells. This depends on the presentation of antigen to the T cell INTERSTITIAL LUNG DISORDERS by an accessory cell. Such accessory cells are drawn Since the report by Reynolds et a122 of the variety of from the mononuclear phagocyte system.'6 The local inflammatory cells obtained by lavage of the antigen to be presented may be processed by the lungs of patients with interstitial lung disease, the macrophage and then "presented" to the lympho- technique of bronchoalveolar lavage has beome a on October 1, 2021 by guest. Protected copyright. cyte on the cell surface of the macrophage. An valuable tool in the development of our understand- essential prerequisite of antigen presentation is the ing of these diseases and is in use in many centres concomitant expression of la self antigens, which are throughout the world. The technique has been used coded by the major histocompatibility complex. This most intensively to identify further the cells which dual antigen expression is vital to the activation of produce the inflammatory response in fibrosing the T lymphocyte and without it immune respon- alveolitis and sarcoidosis.23 24 An excess of neutro- siveness is lost. There are several factors which can phils and eosinophils is found in the former, whereas increase the expression of Ia antigen, particularly T the latter disease is characterised by an excess of cell lymphokines-for example, 'y interferon," while lymphocytes in the lavage fluid. This has given rise class E prostaglandins and a fetoprotein can both to the idea that fibrosing alveolitis is a "neutrophil reduce the expression of Ia antigens."618 alveolitis" and sarcoidosis a "lymphocyte In man the DR antigen is the equivalent of the Ia alveolitis."25 26 These terms identify quite appropri- antigen in the mouse. There have now been several ately which cells are present in abnormal propor- reports that alveolar macrophages obtained by lav- tions in bronchoalveolar lavage from patients with age from patients express the DR antigen and that these disorders, but there is a danger that their use this expression is enchanced in such disorders as may obscure the importance of the other inflammat- fibrosing alveolitis and sarcoidosis.19 There have, ory cells that are present. For example, the Thorax: first published as 10.1136/thx.40.5.321 on 1 May 1985. Downloaded from 325 eosinophil may be plentiful in fibrosing alveolitis monocytes to the inflammatory response and this and excess lymphocytes may also be found in the amplification produces the building blocks on which lung lavage returns.23 Furthermore, in sarcoidosis the granulomas are formed. Macrophages obtained that has advanced to a fibrotic state the neutrophil is by lavage from patients with sarcoidosis, like those also prominent in bronchoalveolar lavage fluid.27 from patients with fibrosing alveolitis, secrete The alveolar macrophage remains the most increased amounts of fibronectin30 and alveolar numerous cell obtained from lavage in almost all macrophage derived growth factor.3' It is not clear diseases except hypersensitivity pneumonitis. Mor- why the fibrotic response in sarcoidosis is not as phological examination of macrophages retrieved by pronounced as in interstitial pulmonary fibrosis. bronchoalveolar lavage plays a small part in the Despite these considerable contributions to under- diagnosis of diffuse parenchymal lung disease. Iron standing derived from lavage studies, important containing macrophages are found in pulmonary questions still require answers. For example, the haemosiderosis, characteristic X bodies within mac- relative contributions of neutrophils and mac- rophages are revealed by electron microscopy in his- rophages to tissue damage are not known and the tiocytosis X, and lamellar bodies in lavage fluid and control of fibroblast proliferation and collagen within macrophages are diagnostic of pulmonary synthesis are understood only partially. Further- alveolar proteinosis. Until relatively recently the more, the complex interrelationships between the functional role of the macrophage in disease has various cell types that produce granulomas in one been ignored, but an important series of studies disease and extensive fibrosis in another need from Crystal's laboratory in the United States has further clarification. It is tempting to suggest that produced evidence suggesting that the macrophage with clearer definition of the subpopulations of mac- has a central role in the pathogenesis of both fibros- rophage it will be possible to subdivide function as ing alveolitis and sarcoidosis (for reviews see 25 and well as phenotype and that a clearer picture of the 26). In fibrosing alveolitis macrophages obtained by cell biology of these disorders will emerge. One lavage have been shown to secrete spontaneously important criticism of the study of lavage mac- both a high and a low molecular weight neutrophil rophages in the exploration of the pathogenesis of chemotactic factor.2829 It is now believed that cir- interstitial disorders is based on the suggestion that culating immune complexes stimulate the mac- these lavage cells may not accurately reflect the rophage to produce neutrophil chemotactic factors, function of cells present in the interstitium. So far which in turn attract neutrophils into the lung. Then this problem has not been addressed satisfactorily, http://thorax.bmj.com/ the neutrophil, it is suggested, discharges oxygen but by using a range of monoclonal antibodies to radicles and proteases, which damage the cellular provide accurate phenotypes of the lavage popula- and connective tissue framework of the interstitium. tions it should be possible to provide an answer. This gives rise to further macrophage activation, thereby amplifying the inflammatory process. As the macrophage is capable of protease secretion and SMOKING AND THE ALVEOLAR MACROPHAGE oxygen radicle production, however, the relative Cigarette smoking has several extremely important contributions of these two cells to tissue damage effects on the alveolar macrophage. Firstly, the have not yet been elucidated. The macrophage is numbers of macrophages obtained by lavage are on October 1, 2021 by guest. Protected copyright. also responsible for the production of alveolar mac- some four to six times greater in smokers than in rophage derived growth factor and fibronectin. non-smokers.34 Morphologically the macrophages These are respectively progression and competence contain increased amounts of pigment and charac- factors stimulating fibroblasts to replicate, and their teristic inclusions may be identified by light and elec- production is triggered by lymphokines. Mac- tron microscopy. There is an increased resting rophages obtained by lavage from patients with metabolism of glucose by macrophages from smok- interstitial fibrosis spontaneously secrete excess ers and an increased generation of oxygen radicles. quantities of both growth factor and fibronectin."3' Intracellular levels of lysosomal enzymes such as In sarcoidosis the study of lavage macrophages acid phosphatase, f3 glucuronidase are significantly has also aided understanding of the pathogenetic higher and elastase secretion is increased (for review mechanisms underlying the granulomatous see 35). Enhanced macrophage secretory capacity response. Lavage macrophages spontaneously sec- may be important in the pathogenesis of certain lung rete interleukin- 1,32 which is thought to activate T conditions, notably emphysema. Clearly the effects lymphocytes to synthesise interleukin-233; this in of cigarette smoking on the macrophages retrieved turn may activate other T lymphocytes to produce by lavage must be borne in mind in the design of lymphokines, including monocyte chemotactic fac- studies comparing macrophages obtained from dif- tor. It is suggested that this results in recruitment of ferent groups of patients. Thorax: first published as 10.1136/thx.40.5.321 on 1 May 1985. Downloaded from 326 THE ALVEOLAR MACROPHAGE AND EMPHYSEMA Thus there appear to be several factors that may Emphysema is associated with loss of lung elasticity. be relevant to the pathogenesis of emphysema, and The fashionable theory of the pathogenesis of the simple theory of an imbalance between neut- emphysema suggests that an imbalance exists bet- rophil elastase and a1 proteinase inhibitor is almost ween neutrophil secreted elastase (serine elastase) certainly not the whole story. Clearly the mac- and the major inhibitor of neutrophil serine elastase, rophage could have more than one role in the a1 proteinase inhibitor (al antitrypsin) within lung development of this disease. tissue.36 Evidence supporting this hypothesis is the presence of excess neutrophils in the lung lavage * * fluid obtained from cigarette smokers and the finding of inactive ca, proteinase inhibitor in The macrophage has a large range of functional cigarette smokers' lavage fluid. The exact mechan- capacity and the advent of bronchoalveolar lavage ism whereby the neutrophil is stimulated to secrete has focused attention on the human alveolar mac- its serine elastase is not clear. rophage. This atraumatic means of obtaining mac- The macrophage is, however, capable of secreting rophages has facilitated the diagnosis of conditions its own elastase, a metalloenzyme, which differs such as histiocytosis X and alveolar proteinosis, has from its neutrophil counterpart by not being inhi- improved our understanding of several other lung bited by a1 proteinase inhibitor37 and it is of interest conditions, and still holds promise for the future, that smokers' macrophages obtained by lavage sec- particularly if subgroups of macrophages can be rete more elastase than those obtained from non- identified and separated for functional study. smokers.38 At present, the major metalloenzyme inhibitor is thought to be a2 macroglobulin, although RM DU BoIS it seems possible that a tissue metalloenzyme Royal Free Hospital inhibitor may exist within the lung. Alpha2 macro- London globulin is notable for its absence from lung lavage fluid despite its presence in serum. Its role in the inhibition, within the lung, of macrophage derived I am pleased to acknowledge the help and criticism elastase is not known. Macrophages may also of Dr LW Poulter and Dr DA Campbell in the prep- release neutrophil elastase and a, proteinase aration of this manuscript, and I am grateful to Miss inhibitor previously phagocytosed as complexes.

E Hogg for her expert secretarial assistance. http://thorax.bmj.com/ Other inhibitors of proteinase activity may be found in lung secretions, especially a, antichymo- trypsin39 and bronchial mucous proteinase References inhibitor.40 Alpha, antichymotrypsin is an inhibitor of the neutrophil proteinase cathepsin G and has 1 Metchnikoff E. LeVons sur la pathologie comparee de been shown to be secreted by human alveolar mac- l'inflammation. Paris: Masson, 1891 (Republished by in vitro.39 Bronchial mucous proteinase Dover Publications, 1968). rophages 2 van Furth R, Cohn ZA, Hirsch JG, Humphrey JH, inhibitor is found predominantly in the upper air- Spector WG, Langevoort HL. The mononuclear ways and is a powerful inhibitor of neutrophil elas- phagocyte system. A new classification of mac- on October 1, 2021 by guest. Protected copyright. tase and cathepsin G. rophages, monocytes and their precursor cells. Bull Finally, there is evidence of antiprotease inactiva- WHO 1972;46:845-52. tion in vivo.4' Inactive proteinase inhibitor has 3 Hoefsmit ECM, Duijvestijn AM, Kamperdijk EWA. ca, Relation between Langerhans cells, veiled cells and been recognised in the lung lavage fluid obtained interdigitating cells. Immunobiology 1982;161:255- from patients who smoke. This inactivation is 65. believed to be due to oxidation of the methionine 4 Blusse van oud Alblas A, van Furth R. The origin of residue at the active site of the proteinase inhibitor. pulmonary macrophages. Immunobiology Cigarette smoke contains oxidant radicals and also 1982; 161:186-92. stimulates the generation of free oxygen radicals by 5 Thomas ED, Ramberg RE, Sale GE, Sparkes RS, Golde DW. Direct evidence for a bone marrow origin macrophages. Either or both of these mechanisms of the alveolar macrophage in man. Science may be relevant to the inhibition of a, proteinase 1976; 192:1016-8. inhibitor in vivo. Furthermore, a1 proteinase 6 Mackaness GB. The mechanism of macrophage activa- inhibitor can be cleaved by the metalloenzyme, and tion. In Mudd S, ed. Infectious agents and host reac- even the formation of complexes of neutrophil elas- tions. Philadelphia: WB Saunders, 1970:61-75. not 7 Adams DO, Hamilton TA. The cell biology of mac- tase with a proteinase inhibitor may guarantee rophage activation. Ann Rev Immunol 1984; 2: 283- inactivation as a2 macroglobulin-neutrophil elastase 318. complexes still retain some enzyme activity. 8 Weissman D, Banks D, Barkman HW, Newton J, de Thorax: first published as 10.1136/thx.40.5.321 on 1 May 1985. Downloaded from

327 Shazo RD. Evidence for immunologic dysfunction at of the lower respiratory tract. N Engl J Med the lung level in patients with squamous cell carcinoma 1984;310: 154-66. of the lung. Am Rev Respir Dis 1984;129:A31 (abs- 26 Crystal RG, Bitterman PB, Rennard SI, Hance AJ, tract). Keogh BA. Interstitial lung disease of unknown cause: 9 Green GM, Jakab GJ, Low RB, Davis GS. Defense disorders characterized by chronic inflammation of the mechanisms of the respiratory membrane. Am Rev lower respiratory tract. N Engl J Med 1984;310:235- Respir Dis 1977; 115:479-514. 44. 10 Nacy CA, James SL, Osler CN, Meltzer MS. Activa- 27 Haslam PL, Coutts II, Watling AF, et al. Bronchoal- tion of macrophages to kill Rickettsiae and Leish- veolar lavage features associated with radiographic mania. Contemp Top Immunobiol 1984; 14:147-70. evidence of fibrosis in pulmonary sarcoidosis. In: Chre- 11 Johnson WJ, Somers SD, Adams DO. Activation of tien J, Marsac J, Saltiel JC, eds. Sarcoidosis and other macrophages for tumour cytotoxicity. Contemp Top granulomatous disorders. Paris: Pergamon Press, Immunobiol 1983; 14:127-46. 1983:209-15. 12 Nathan C, Cohn Z. Role of oxygen-dependent 28 Merrill WW, Naegel GP, Matthay RA, Reynolds HY. mechanisms in antibody-induced lysis of tumour cells Alveolar macrophage-derived chemotactic factor: by activated macrophages. J Exp Med 1980; 152:198- kinetics of in vitro production and partial characteriza- 208. tion. J Clin Invest 1980;65:268-76. 13 Swinburne S, Moore M, Cole P. Human bronchoalveo- 29 Hunninghake GW, Gadek JE, Fales HM, Crystal RG. lar macrophage cytotoxicity for cultured human lung- Human alveolar macrophage-derived chemotactic fac- tumour cells. Br J Cancer 1982;46:625-34. tor for neutrophils: stimuli and partial characterization. 14 Vose BM. Cytotoxicity of adherent cells associated J Clin Invest 1980;66:473-83. with some human tumours and lung tissues. Cancer 30 Rennard SI, Hunninghake GW, Bitterman PB, Crystal Immunol Immunother 1978;5: 173-9. RG. Production of fibronectin by the human alveolar 15 Lemarie E, Caffe P, Legrand MF, et al. Alveolar mac- macrophage: mechanism for the recruitment of fibro- rophage dysfunction in malignant lung tumours. blasts to sites of tissue injury in interstitial lung dis- Thorax 1984;39:448-52. eases. Proc Natl Acad Sci USA 1981;78:7147-51. 16 Unanue ER, Beller DI, Lu CY, Allen PM. Antigen 31 Bitterman PB, Adelberg S, Crystal RG. Mechanisms of presentation: comments on its regulation and mechan- pulmonary fibrosis: spontaneous release of the alveolar ism. J Immunol 1984; 132:1-5. macrophage-derived growth factor in the interstitial 17 Steeg PS, Moore RN, Johnson HM, Oppenheim JJ. lung disorders. J Clin Invest 1983;72: 1801-13. Regulation of murine macrophage Ia antigen expres- 32 Hunninghake GW. Release of Interleukin-1 by alveo- sion by a lymphokine with immune interferon activity. lar macrophages of patients with active pulmonary sar- J Exp Med 1982;156:1780-93. coidosis. Am Rev Respir Dis 1984; 129:569-72. 18 Snyder DS, Beller DI, Unanue ER. Prostaglandins 33 Pinkston P, Bitterman PB, Crystal RG. Spontaneous modulate macrophage Ia expression. Nature

release of interleukin-2 by lung T lymphocytes in http://thorax.bmj.com/ 1982;299: 163-5. active pulmonary sarcoidosis. N Engl J Med 19 Razma AG, Lynch JP, Wilson BS, Ward PA, Kunkel 1983;308:793-800. SL. Expression of Ia-like (DR) antigen on human 34 Harris JO, Swenson EW, Johnson JE. Human alveolar alveolar macrophages isolated by bronchoalveolar lav- macrophages: comparison of phagocytic ability, glu- age. Am Rev Respir Dis 1984;129:419-24. cose utilization and ultrastructure in smokers and 20 Poulter LW. Antigen presenting cells in situ: their non-smokers. J Clin Invest 1970;49:2086-96. identification and involvement in immunopathology. 35 Hunninghake GW, Gadek JE, Kawanami 0, Ferrans Clin Exp Immunol 1983;53:513-20. VJ, Crystal RG. Inflammatory and immune processes 21 Campbell DA, Poulter LW, Janossy G, du Bois RM. in the human lung in health and disease: evaluation by Immunohistological analysis of lung tissue from bronchoalveolar lavage. Am J Pathol 1979;97: 149- patients with cryptogenic fibrosing alveolitis suggests 206. on October 1, 2021 by guest. Protected copyright. local expression of immune hypersensitivity. Thorax 36 Cohen AB, Rossi M. Neutrophils in normal lungs. Am (in press). Rev Respir Dis 1983;127:S3-S9. 22 Reynolds HY, Fulmer JD, Kazmierowski JA, Roberts 37 Niederman MS, Fritts LL, Merrill WW, et al. Demon- WC, Frank MM, Crystal RG. Analysis of cellular and stration of a free elastolytic metalloenzyme in human protein content of bronchoalveolar lavage fluid from lung lavage fluid and its relationship to alpha,, patients with idiopathic pulmonary fibrosis and chronic antiprotease. Am Rev Respir Dis 1984; 129:943-7. hypersensitivity pneumonitis. J Clin Invest 38 Rodriguez RJ, White RR, Senior RM, Levine EA. 1977;59: 165-75. Elastase release from human alveolar macrophages: 23 Haslam PL, Turton CWG, Lukoszek A, etal. Bron- comparison between smokers and non-smokers. Sci- choalveolar lavage fluid cell counts in cryptogenic ence 1977;198:313-4. fibrosing alveolitis and their relation to therapy. 39 Burnett D, McGillivray DH, Stockley RA. Evidence Thorax 1980;35:328-39. that alveolar macrophages can synthesize and secrete 24 Weinberger SE, Kelman JA, Elson NA, etal. Bron- alpha,-antichymotrypsin. Am Rev Respir Dis choalveolar lavage in interstitial disease. Ann Intern 1984; 129:473-6. Med 1978;89:459-66. 40 Janoff A, Carp H, Laurent P, Raju L. The role of 25 Crystal RG, Bitterman PB, Rennard SI, Hance AJ, oxidative processes in emphysema. Am Rev Respir Dis Keogh BA. Interstitial lung diseases of unknown 1983; 127:S31-8. cause: disorders characterized by chronic inflammation