Exaggerated spontaneous release of platelet-derived growth factor by alveolar macrophages from patients with idiopathic pulmonary fibrosis

mRNA phenotyping for studying gene expression in small numbers of cells: platelet-derived growth factor and other growth factors in wound-derived macrophages

The understanding of biologic and pathophysiologic processes in lung is aided by a technique for ascertaining the transcriptional phenotype of small numbers of cells examined in vivo. The mRNA phenotyping procedure consists of scaled-down methods for isolating mRNA from small numbers of cells, followed by reverse transcription of the RNA and specifically primed amplification of the cDNA by the polymerase chain reaction. We show an example of the use of the technique in a study of expression of platelet-derived growth factor and other growth factor genes in macrophages isolated from wound cylinders implanted in mice. With this technique, the transcriptional phenotype of purified normal lung epithelial and mesenchymal cells, macrophages, or cells obtained from lavaged lungs or punch biopsy specimens can be examined as a rapid first step in understanding molecular processes in the lung.

Bronchoalveolar lavage

The technique of BAL performed through the fiberoptic bronchoscope has, in two decades, provided clinicians and researchers with the ability to safely sample the inflammatory-immune cell milieu of the human lung. Standardized BAL and processing of the lavage constituents provides assistance in determining the optimal care of patients with a variety of lung diseases, and renders diagnosis in selected cases. It has become indispensable in the diagnosis of pulmonary infiltrates in immunocompromised patients, and plays an important role in improving clinical management. Finally, it continues to yield an ever increasing amount of data for the researchers studying the mechanisms and pathogenesis of lung disease. It is likely that BAL will become an even more valuable tool with increasing relevance to the practice of chest medicine in the 1990s.

Activation of cultured rat hepatic lipocytes by Kupffer cell conditioned medium. Direct enhancement of matrix synthesis and stimulation of cell proliferation via induction of platelet-derived growth factor receptors

Hepatic lipocytes appear to be central to the pathogenesis of hepatic fibrosis, undergoing activation during inflammation to a matrix-producing, proliferative cell type. We have studied the activation process in culture by examining the response of lipocytes to conditioned medium from hepatic macrophages (Kupffer cells). Lipocytes exposed to Kupffer cell medium (KCM) exhibited cellular and nuclear enlargement associated with up to a threefold increase in collagen and total protein synthesis per cell. Cell proliferation was also stimulated as measured by [3H]thymidine incorporation and direct cell counting. The latter effect was serum dependent and inhibited by antibodies to platelet-derived growth factor (PDGF). Proliferation could be stimulated by recombinant PDGF, but only after preincubation of cells with KCM. These findings suggested that KCM was eliciting expression of the PDGF receptor in lipocytes, and this was confirmed by immunoblot analysis with antibodies to the PDGF receptor. DNA synthesis in lipocytes exposed to KCM occurred at 48 h, which reflected the time required for PDGF receptor expression (24 h) plus initiation of [3H]thymidine incorporation (24 h). These results indicate that KCM has multiple stimulatory effects on cultured lipocytes similar to activation of these cells observed in vivo.

Polyamines and epidermal growth factor in monocrotaline-induced pulmonary hypertension

Multiple lines of evidence suggest that the polyamines, a family of low-molecular-weight organic cations with documented regulatory note in cell growth and differentiation, are involved with hyperplastic and hypertrophic responses of lung cells underlying hypertensive pulmonary vascular disease. Little is known, however, of the factor(s) initiating polyamine synthesis in pulmonary hypertension. This study tested the key aspects of the hypothesis that augmented polyamine synthesis, and attendent vascular structural alterations in monocrotaline (MCT)-treated rats can be ascribed to elaboration of an epidermal growth factor (EGF)-like mitogen. In lungs of rats treated 4 days previously with 60 mg/kg, EGF-like immunoreactivity was detected diffusely throughout perivascular regions. Intravenous administration of human recombinant EGF (125 pg/h) to rats for 1 wk was associated with medial thickening in pulmonary arteries between 100 and 200 microns in diameter, significant increases in lung polyamine contents, and a moderate elevation in mean pulmonary arterial pressure. These observations indicate that EGF can be detected in the lungs of MCT-treated rats and that exogenous EGF mimics some of the action of MCT on the rat lung. It is thus reasonable to speculate that an EGF-like mitogen may participate in the response to MCT in part through a polyamine-dependent mechanism.

Epidermal growth factor augments reactivity to angiotensin II in the rat pulmonary circulation

To determine if epidermal growth factor (EGF), a vascular smooth muscle mitogen exhibiting systemic vasoactivity, causes constriction or dilation of the pulmonary vascular bed, this study evaluated the actions of EGF in isolated, buffer-perfused rat lungs and in isolated rat pulmonary arteries. In perfused rat lungs with baseline vasomotor tone, EGF administered at bolus doses of 10(-9) to 3 x 10(-7) M failed to exert either constrictor or dilator actions or to promote edema formation as evidenced by a constant lung wet-to-dry-weight ratio. Elevation of baseline tone with either prostaglandin (PG)F2 alpha or angiotensin II also failed to unmask an effect of EGF on pulmonary vascular resistance. In contrast to these negative observations, pretreatment with 5 x 10(-8) M EGF consistently augmented pressor responses evoked by angiotensin II. Constrictor responses to potassium chloride and to PGF2 alpha were unaffected by EGF pretreatment. In isolated rat extrapulmonary arteries, EGF provoked contraction in 40% of the preparations studied. Responsive vessels exhibited maximal EGF-induced contractions that were approximately 25% of that associated with angiotensin II and were characterized by an ED50 of 7 x 10(-8) M. Relaxant activity of EGF could not be demonstrated in isolated arterial preparations with normal resting tone or with tone elevated by addition of norepinephrine to the tissue bath. Endothelial denudation also failed to unmask contractile or relaxant effects of EGF. Similar to its actions in isolated, perfused rat lungs, EGF potentiated contractions of isolated pulmonary arteries induced by angiotensin II.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet-derived growth factor and transforming growth factor-beta enhance tissue repair activities by unique mechanisms

Platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) markedly potentiate tissue repair in vivo. In the present experiments, both in vitro and in vivo responses to PDGF and TGF-beta were tested to identify mechanisms whereby these growth factors might each enhance the wound-healing response. Recombinant human PDGF B-chain homodimers (PDGF-BB) and TGF-beta 1 had identical dose-response curves in chemotactic assays with monocytes and fibroblasts as the natural proteins from platelets. Single applications of PDGF-BB (2 micrograms, 80 pmol) and TGF-beta 1 (20 micrograms, 600 pmol) were next applied to linear incisions in rats and each enhanced the strength required to disrupt the wounds at 5 d up to 212% of paired control wounds. Histological analysis of treated wounds demonstrated an in vivo chemotactic response of macrophages and fibroblasts to both PDGF-BB and to TGF-beta 1 but the response to TGF-beta 1 was significantly less than that observed with PDGF-BB. Marked increases of procollagen type I were observed by immunohistochemical staining in fibroblasts in treated wounds during the first week. The augmented breaking strength of TGF-beta 1 was not observed 2 and 3 wk after wounding. However, the positive influence of PDGF-BB on wound breaking strength persisted through the 7 wk of testing. Furthermore, PDGF-BB-treated wounds had persistently increased numbers of fibroblasts and granulation tissue through day 21, whereas the enhanced cellular influx in TGF-beta 1-treated wounds was not detectable beyond day 7. Wound macrophages and fibroblasts from PDGF-BB-treated wounds contained sharply increased levels of immunohistochemically detectable intracellular TGF-beta. Furthermore, PDGF-BB in vitro induced a marked, time-dependent stimulation of TGF-beta mRNA levels in cultured normal rat kidney fibroblasts. The results suggest that TGF-beta transiently attracts fibroblasts into the wound and may stimulate collagen synthesis directly. In contrast, PDGF is a more potent chemoattractant for wound macrophages and fibroblasts and may stimulate these cells to express endogenous growth factors, including TGF-beta, which, in turn, directly stimulate new collagen synthesis and sustained enhancement of wound healing over a more prolonged period of time.

Quartz exposure, retention, and early silicosis in sheep

The purposes of this study were (1) to investigate the chronology of events in cellular and biochemical changes thought to be important in the development of silicosis, (2) to relate these to changes in lung function and radiograph, and (3) to evaluate the relation of quartz exposure and retention to individual response leading to early silicosis. Thirty-six sheep were exposed by repeated intratracheal infusion at 10-day intervals to 100 mg Minusil-5 in 100 ml saline (Si group), and 10 sheep were exposed at the same intervals to 100 ml saline (control). All sheep were investigated at 3-month intervals by chest radiograph, lung function, and lung lavage. At month 9, chest radiograph score of parenchymal opacities was significantly increased at 2.8 +/- 0.6 versus 0.4 +/- 0.4 in the Si group (p less than .05), establishing early radiologic silicosis. Lung function was significantly altered with reduction in lung compliance, vital capacity, and diffusion capacity (p less than .05). Lung lavage cellularity revealed significant increase in total cells (X 2.5), macrophages (X3), and neutrophils (X3). Albumin in BAL remained at the control level. Fibronectin production was significantly increased, as was the fibroblast growth activity, without significant change in procollagen 3 at this early stage of disease. Total phospholipids were significantly elevated in the Si-exposed sheep, and the profile demonstrated an increase in all the phospholipid components. Spontaneous release of hydrogen peroxide by alveolar cells was not increased, but in the presence of phorbol myristate acetate (PMA) higher levels of peroxide were found in the quartz-exposed sheep (p less than .05). The cellular and biochemical alterations of lung lavage preceded other changes. At month 12, there were good correlations (r greater than .49, p less than .001) between parameters evaluating related phenomena but poor correlations between measurements evaluating different aspects of the disorder. To investigate the heterogeneity in the individual response of sheep to the same exposure (susceptibility), individual quartz retention levels at month 12 were measured and found to correlate well with individual parameters of disease activity. We concluded that in early silicosis of sheep, cellular and biochemical changes in lung lavage preceded derangements of pulmonary function and radiographic abnormalities. Thereafter, parameters of lung lavage, lung function, and radiograph were significantly interrelated, but for a given exposure the degree of quartz retention appeared to determine the intensity of the silicotic process.

Differential regulation of collagen, glycosaminoglycan, fibronectin, and collagenase activity production in cultured human adult dermal fibroblasts by interleukin 1-alpha and beta and tumor necrosis factor-alpha and beta

In order to clarify the role played by immunologically derived cytokines in dermal connective tissue synthesis and degradation, we investigated the effect of human recombinant (hu-r) interleukin (IL) 1-alpha and beta, hu-r tumor necrosis factor (TNF)-alpha and beta, hu-r IL 2, and hu-r granulocyte-macrophage colony-stimulating factor (GM-CSF) on the production of collagen, glycosaminoglycan, fibronectin, and collagenase activity by three lines of cultured human adult dermal fibroblasts. Our results show that 24-72 h treatment of confluent fibroblast cultures with IL 1-alpha or beta or TNF-alpha or beta causes concentration (1 to 1 X 10(4) U/ml) dependent increases in collagen, glycosaminoglycan, and collagenase activity production, but decreases in fibronectin production. In contrast, treatment with IL 2 and GM-CSF had no effect on fibroblast functions. The data show that IL 1-alpha and beta and TNF-alpha and beta differentially regulate fibroblast functions, and that increases in catabolic functions like collagenase activity production are more than tenfold greater than increases in anabolic functions like collagen production. When these results are considered along with other reports, they suggest that IL 1 and TNF may play predominately a catabolic role in situ during dermal fibrotic responses by directly inhibiting fibronectin production and indirectly causing the degradation of collagen and glycosaminoglycan by significantly increasing dermal fibroblast elaboration of collagenase and proteoglycanase activities.

Correlation of fibrosis and transforming growth factor-beta type 2 levels in the eye

Approximately 1 out of every 10 eyes undergoing surgery for retinal detachment develops excessive intraocular fibrosis that can lead to traction retinal detachment and ultimate blindness. This disease process has been termed proliferative vitreoretinopathy (PVR). The ability to monitor and grade this fibrotic response accurately within the eye as well as the ability to aspirate vitreous cavity fluid bathing the fibrotic tissue makes this an ideal setting in which to investigate the development of fibrosis. Although laboratory studies have recently shown that transforming growth factor-beta (TGF-beta) can enhance fibrosis, little clinical evidence is yet available correlating the level of this or other growth factors with the degree of fibrosis in a clinical setting. We have found that vitreous aspirates from eyes with intraocular fibrosis associated with PVR have more than three times the amount of TGF-beta (1,200 +/- 300 pM [SEM]) found in eyes with uncomplicated retinal detachments without intraocular fibrosis (360 +/- 91 pM [SEM]). Using an in vitro assay, 84-100% of the TGF-beta activity could be blocked with specific antibodies against TGF-beta 2, whereas only 10-21% could be blocked by specific antibodies against TGF-beta 1. TGF-beta 1 was used in an animal model of traction retinal detachment. Since beta 1 and beta 2 have essentially identical biologic effects and only human beta 1 was available in quantities required, beta 1 was chosen for these in vivo studies. The injection of TGF-beta1 plus fibronectin (FN) but not TGF-beta1 alone into the vitreous cavity of rabbits resulted in the increased formation of intraocular fibrosis and traction retinal detachments as compared to control eyes. In previous studies, intravitreal FN levels were also found to be elevated in eyes with intraocular fibrosis.

Experimental pulmonary fibrosis induced by paraquat plus oxygen in rats: a morphologic and biochemical sequential study

Changes in lung structure and collagen metabolism were studied at 1, 2, 3, 4, 6, and 8 weeks in a model of pulmonary fibrosis induced in rats with paraquat plus hyperoxia. Morphologic examination of the lungs revealed that the earliest lesions consisted of severe and irreversible endothelial and alveolar epithelial cell damage. Afterward, an inflammatory process took place, initially dominated by polymorphonuclear leukocytes and then by mononuclear cells, but with the constant presence of granulocytes. From the fourth week on there were fibroblast proliferation and a moderate increase of mast cells. In the early stages alveolitis was focal, but from the second week the lungs were diffusely affected with severe distortion of the architecture. Collagen content was moderately increased in the first 2 weeks and then showed a progressive increment until the end of the experiment. Collagen synthesis was significantly elevated from the fourth week, coinciding with interstitial fibroblast proliferation, although there were some animals that showed increased collagen production from the first week. Collagenolytic activity occurred in 3 stages: at 2 weeks there was increased collagen degradation, at 3, 4, and 6 weeks the values showed a trimodal behavior, and at 8 weeks almost all experimental rats presented an important decrease of collagenolysis. Thus, the development of lung fibrosis was associated first with increased rates of collagen synthesis and later with a decrease of collagen degradation.

The contribution of alveolar macrophages to hyperreactive airway disease

Thus, there is substantial evidence that favors a role for macrophages in subjects with atopic asthma. The precise manner in which these cells participate and the relative degree to which these cells contribute to, or orchestrate, events remains to be delineated. Research on the potential role of macrophages in asthma syndromes remains in its infancy. In time we will discover new roles for mononuclear phagocyte-derived mediators and many more new mediators that will play a role in the complex immunologic events ongoing in the airways of patients with asthma. Also, future research will continue to explore what promises to be a productive area of research, namely, cell-cell interactions and the manner in which many cells participate together in the pathophysiology of asthma. If macrophages can be demonstrated to influence airway inflammation associated with atopic disease, they may be appropriate targets for therapeutic intervention.

Hyaluronan and type III procollagen peptide concentrations in bronchoalveolar lavage fluid in idiopathic pulmonary fibrosis

The connective tissue components hyaluronan (hyaluronic acid) and type III procollagen peptide were measured in bronchoalveolar lavage fluid in 22 patients with idiopathic pulmonary fibrosis and 21 healthy control subjects. The patients with idiopathic pulmonary fibrosis had higher concentrations of hyaluronan (median 46 micrograms/l) and type III procollagen peptide (median 0.45 micrograms/l) than the healthy controls (9 and less than 0.02 micrograms/l; p less than 0.001). The patients had normal serum concentrations of hyaluronan and of the procollagen peptide, and albumin concentrations in lavage fluid similar to those of the control subjects. Neutrophil and lymphocyte counts in lavage fluid were increased on average 10 and two fold respectively in the patients with idiopathic pulmonary fibrosis and both correlated with the amount of hyaluronan recovered (p less than 0.05). An inverse correlation was seen between the transfer factor for carbon monoxide and hyaluronan concentrations in lavage fluid in the patients (p less than 0.05). Deterioration in lung function and radiographic progression were seen over six months in 12 of the patients. These patients had higher lavage fluid concentrations of hyaluronan and type III procollagen peptide than the patients whose disease was stable (p less than 0.01). Increased synthesis of hyaluronan and type III procollagen peptide in lung parenchyma may reflect activation or proliferation (or both) of pulmonary fibroblasts in idiopathic pulmonary fibrosis and seems to be linked to the severity and activity of the lung disease.

Immunohistologic demonstration of platelet-derived growth factor (PDGF) and sis-oncogene expression in scleroderma

Although the pathogenesis and mechanisms responsible for excessive connective tissue deposition are not known, it has been thought that specific growth factors may have an effect on scar formation by increasing the fibroblast population and by affecting the amount and types of matrix synthesized. In this regard, we explored the appearance and localization of TGF alpha, TGF beta, PDGF, and sis-onc expression in situ. Sections of skin biopsies from eight scleroderma patients were investigated using specific antibodies to TGF alpha, TGF beta, human PDGF, and sis-onc products for immunohistochemistry. Most significantly, deposition of PDGF was detected in the endothelial lining of small capillaries in association with certain mononuclear cells of the perivascular infiltrates. In particular, strong labeling was observed in the cytoplasm of macrophages. Smooth muscle also appeared to be specifically labeled. Similarly, sis-onc product localized in the same areas. No significant staining was observed with antibodies to TGF alpha. TGF beta was found rather diffusely throughout the dermal connective tissue and was only occasionally observed in capillaries of lesions. We conclude that the PDGF may play an important role in the pathogenesis of scleroderma.

Idiopathic pulmonary fibrosis: cellular and molecular pathogenesis

Diffuse involvement of the pulmonary interstitium with abnormal fibrous tissue is a process that occurs in many settings. There are many possible etiologies for pulmonary fibrosis, but in the majority of individuals, a clear cause cannot be determined and a diagnosis of idiopathic pulmonary fibrosis (IPF) results. Despite limited knowledge concerning the etiology, recent advances in biomedical technology offer great promise for increasing our understanding of IPF. This review will focus on current concepts of the pathogenesis and therapy of IPF.

Cellular events in alveolitis and the evolution of pulmonary fibrosis

"Alveolitis", as opposed to "pneumonia" sensu strictiori, is a term used to denote diffuse inflammatory changes of the pulmonary parenchyma, excluding those that result from local bacterial, fungal or other extracellular microbial growth. The various types of alveolitis are classified according to their histological characteristics and range from "luminal phagocytic" or "mural lymphoplasmacellular" and "exudative" to "fibrosing" alveolitis. In this overview, various exogenous and endogenous causes of different types of alveolitis, and the cellular events in their pathogenesis are briefly discussed to illustrate the complex mechanisms involved. Particular emphasis is placed on the possible transition from diffuse exudative to fibrosing alveolitis. It appears that pulmonary fibrosis, which is usually patchy rather than truly diffuse, does not have a uniform pathogenesis. Besides the possibility of a certain degree of a diffuse fibrosis three major pathways are evident: (1) granulation tissue budding into alveolar lumina (luminal fibrosis) (2) exudate incorporation into alveolar walls (mural fibrosis) and--at least equally important--(3) so-called collapse (atelectatic) induration (obliterative-interseptal fibrosis), a process that has largely been neglected so far.

Spontaneous and stimulated release of tumor necrosis factor-alpha (TNF) from blood monocytes of miners with coal workers' pneumoconiosis

It is generally accepted that fibrotic lung diseases are mediated by macrophage-derived cytokines. We investigated the release of the monokine tumor necrosis factor-alpha (TNF) from blood monocytes in a group of 66 coal miners and 12 non-dust-exposed individuals. Twenty-seven miners had simple Coal Workers' Pneumoconiosis (CWP). Control miners (n = 39) were matched with respect to age, years underground, and smoking. Monocytes were assayed for TNF release, spontaneously or in response to soluble (endotoxin) or particulate (coal mine dust, silica) stimulation. TNF was measured with a TNF-specific ELISA. Monocytes of all subjects responded to stimulants by the release of TNF. Dust-exposed controls' monocytes revealed higher TNF release as compared to normal controls. The greatest discriminator between control miners and cases (CWP) was coal mine dust-induced TNF release. Interestingly, the largest difference was observed between controls and those cases with a small number of opacities (0/1, 1/0, 1/1, and 1/2), giving an odds ratio of 6.3 to find an individual with a "high" dust-induced TNF release in the patient group.

Plasma somatomedin-C levels in systemic sclerosis

We have measured the plasma levels of somatomedin-C (SM-C) or insulin-like growth factor I (IGF-I) in 13 patients with progressive systemic sclerosis (PSS) and age and sex matched healthy controls. We found the plasma SM-C levels to be within normal limits in all the patients. Thus, if somatomedin-C plays a role in the pathogenesis of PSS, it is more likely to be at the fibroblast receptor level or in the synthetic response of fibroblasts to SM-C.

Alveolar macrophages release an insulin-like growth factor I-type molecule

Human alveolar macrophages, when activated, release a progression-type growth factor for fibroblasts that signals "competent" fibroblasts to replicate. The present study demonstrates that this growth activity is an insulin-like growth factor I (IGF-I)-type molecule. Partial purification of medium conditioned by activated alveolar macrophages using ion exchange and gel filtration chromatography revealed an IGF-I molecule as detected by an anti-IGF-I polyclonal antibody and that the specific activity of the progression-type growth activity tracked with the amount of IGF-I present. In a serum-free complementation test, the increase in fibroblast proliferation by alveolar macrophage IGF-I was reduced in a dose-response manner with an anti-IGF-I monoclonal antibody. The alveolar macrophage IGF-I displaced 125I-IGF-I from its receptor in a binding assay utilizing human lung fibroblasts and it stimulated type I IGF receptors purified from human lung fibroblasts to phosphorylate a tyrosine-containing artificial substrate. In contrast to the 7.6-kD serum IGF-I, gel chromatography revealed that the alveolar macrophage IGF-I had an apparent molecular mass of 26 kD, similar to other tissue IGF-Is. Alveolar macrophages expressed IGF-I mRNA transcripts as detected by solution hybridization using a 32P-labeled riboprobe complementary to exons I-II-III of the IGF-I gene. In the context of the known functions of the family of IGF-I molecules in cell growth, IGF-I released by activated alveolar macrophages may play a role in acute and chronic inflammatory disorders.

Platelet-derived growth factor mRNA detection in human atherosclerotic plaques by in situ hybridization

Platelet-derived growth factor (PDGF) mRNA, and mRNA for its receptor, have been localized to specific cell types within the human atherosclerotic plaque, using in situ hybridization. The predominant cell types found to express PDGF A and B chain mRNA are mesenchymal-appearing intimal cells and endothelial cells, respectively, with little or no expression detected in macrophages. The distribution of PDGF receptor mRNA containing cells was also examined and found to be localized predominantly in the plaque intima.

Production of platelet-derived growth factor-like mitogen by smooth-muscle cells from human atheroma

Proliferation of vascular smooth-muscle cells occurs during the development of atherosclerosis and the remodeling of arteries that accompanies chronic systemic or pulmonary hypertension. To help define the signals that initiate this abnormal growth, we cultured smooth-muscle cells from human atherosclerotic plaques. These cells (n = 9) released material into their culture medium that stimulated the proliferation of aortic smooth-muscle cells to a mean (+/- SD) level 5.1 +/- 1 times that in control medium. Part of this activity was due to molecules that resemble a mitogen first isolated from platelets and known as platelet-derived growth factor (PDGF), since these cells released PDGF measured in a radioreceptor assay (355 +/- 117 pg per milliliter per 48 hours; n = 6) and since anti-PDGF antibody neutralized 38 +/- 7 percent of this mitogenic activity (range, 13 to 60 percent; n = 6 carotid-plaque isolates). Two human genes encode distinct PDGF subunits that form dimers in different combinations to create biologically active PDGF. Cells cultured from human atheroma contained mRNAs for the PDGF A chain (16 of 17 isolates) but none (of 13) that encoded PDGF B chain (the c-sis proto-oncogene product). We conclude that smooth-muscle cells from diseased human arteries can secrete mitogenic activity, some of which resembles PDGF, and that these cells express the gene for the PDGF A chain selectively. This capacity to produce an endogenous, potentially self-stimulatory (autocrine) growth factor may help to explain how replication of smooth-muscle cells can begin, even while the endothelial barrier remains morphologically intact, early in atherogenesis.

Increased procollagen III aminoterminal peptide-related antigens and fibroblast growth signals in the lungs of patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disorder characterized by an increased density of inflammatory cells, fibroblasts, and collagen within the lung parenchyma. To gain insights into the mechanisms leading to the increased density of fibroblasts and altered collagen metabolism in the IPF lung, bronchoalveolar lavage fluid from normal subjects and patients with IPF or sarcoidosis was analyzed for (1) the presence of antigenic material related to the aminoterminal propeptide domain of type III procollagen, and (2) fibroblast growth-promoting activity in the extracellular milieu of the lower respiratory tract. Whereas bronchoalveolar lavage fluid (BALF) type III procollagen aminoterminal peptide-related antigen levels in 59 patients with sarcoidosis were similar to the levels of control subjects (p greater than 0.10), 31 patients with IPF had markedly increased levels (12-fold over controls; p less than 0.025, IPF versus controls; p less than 0.01, IPF versus sarcoidosis). Type III procollagen aminoterminal peptide-related antigen levels correlated with an increase in the ability of BALF to stimulate fibroblast proliferation (p less than 0.05). Furthermore, BALF from patients with IPF markedly stimulated human lung fibroblast proliferation in vitro (199% increase, p less than 0.01), whereas lavage fluid from patients with sarcoidosis and from control subjects did not. The enhanced fibroblast proliferation induced by IPF BALF occurred in the absence of serum and exogenous growth factors, suggesting that both competence- and progression-type growth factors were present in the lavage fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoglobulin G and its function in the human respiratory tract

Immunoglobulin G--which can be subdivided into four classes, each with different functional characteristics--is an important component of the host defense system of the respiratory tract. An excessive amount can be produced or can accumulate after airway irritation (exposure to cigarette smoke) or from immunologic stimulus of B-lymphocyte-plasma cells in types of hypersensitivity and interstitial lung diseases. Specific antibody activity can be identified in organic dust-induced hypersensitivity pneumonitis and asthma that contributes to disease pathogenesis. The availability of opsonic antimicrobial antibodies is essential for optimal function of phagocytes in uptake and containment of bacteria. With an absolute or functional deficiency of IgG, recurrent and chronic types of sinopulmonary infections occur. These extremes of IgG availability, either high levels (presumably excessive) or deficient, are discussed in this review.