Of mice and men: comparative proteomics of bronchoalveolar fluid.

We hypothesised that comparing the protein mixture in bronchoalveolar lavage fluid (BALF) between humans and mice may lead to mechanistic insights into common and divergent pathways that evolved in each species. BALF from four humans and six mice was pooled separately and underwent identical shotgun proteomic analysis. Functional and network analysis was applied to identify overlapping and distinct pathways enriched in the BALF. Follow-up experiments using Western analysis in unpooled BALF samples were performed. We identified 91 unique proteins in human and 117 unique proteins in mouse BALF samples. Functional analysis of the proteins revealed conservation of several key processes between the species, including defence response. Oxidative stress response, however, was selectively enriched only in mouse BALF. Differences in the expression of peroxiredoxin-1, a key member of the defence pathway against oxidative injury, were confirmed between normal human and mouse BALF and in models of lung injury. A computational proteomics approach of mouse and human BALF confirms the conservation of immune and defence-mediated pathways while highlighting differences in response to oxidative stress. These observations suggest that the use of mice models to study human lung disorders should be undertaken with an appreciation of interspecies variability.

Upregulation of alpha(8)beta(1)-integrin in cardiac fibroblast by angiotensin II and transforming growth factor-beta1.

Using a novel pharmacological tool with (125)I-echistatin to detect integrins on the cell, we have observed that cardiac fibroblasts harbor five different RGD-binding integrins: alpha(8)beta(1), alpha(3)beta(1), alpha(5)beta(1), alpha(v)beta(1), and alpha(v)beta(3). Stimulation of cardiac fibroblasts by angiotensin II (ANG II) or transforming growth factor-beta1 (TGF-beta1) resulted in an increase of protein and heightening by 50% of the receptor density of alpha(8)beta(1)-integrin. The effect of ANG II was blocked by an AT(1), but not an AT(2), receptor antagonist, or by an anti-TGF-beta1 antibody. ANG II and TGF-beta1 increased fibronectin secretion, smooth muscle alpha-actin synthesis, and formation of actin stress fibers and enhanced attachment of fibroblasts to a fibronectin matrix. The alpha(8)- and beta(1)-subunits were colocalized by immunocytochemistry with vinculin or beta(3)-integrin at focal adhesion sites. These results indicate that alpha(8)beta(1)-integrin is an abundant integrin on rat cardiac fibroblasts. Its positive modulation by ANG II and TGF-beta1 in a myofibroblast-like phenotype suggests the involvement of alpha(8)beta(1)-integrin in extracellular matrix protein deposition and cardiac fibroblast adhesion.

Dentate hilar mossy cells and somatostatin-containing neurons are immunoreactive for the alpha8 integrin subunit: characterization in normal and kainic acid-treated rats.

Integrins are heterodimeric cell surface receptors composed of different alpha and beta subunits that mediate cell-cell and cell-extracellular matrix interactions. They have been implicated in the regulation of neuronal migration, differentiation, process outgrowth, and plasticity. The alpha8 integrin subunit associates exclusively with the beta1 subunit to form a receptor (alpha8beta1) for fibronectin, vitronectin, tenascin, and osteopontin. In a previous study, we demonstrated that hippocampal dentate hilar neurons are immunoreactive for alpha8. The present study identifies the major types of alpha8-immunoreactive hilar neurons and characterizes the effects of kainic acid-induced seizures on alpha8-immunoreactivity in these cells. Examination of the hilus in normal rats revealed alpha8-immunoreactivity in the somatodendritic compartments of large hilar neurons identified as mossy cells, including a subset of dendritic thorny excrescences that were contacted by large mossy fiber terminals. alpha8-immunoreactivity also was found in approximately 71% of somatostatin-containing hilar cells. Kainic acid-induced seizures dramatically and rapidly altered the levels and distribution of alpha8-immunoreactivity in hilar neurons. After 1.5 h of seizures, alpha8-immunoreactivity in their dendrites was reduced greatly. One day after kainic acid treatment, labeling was diminished throughout the somatodendritic compartments of most hilar cells. This decrease appeared to be transient, since alpha8 labeling returned to normal levels in surviving hilar neurons within 2 weeks of treatment. In addition, many alpha8-immunoreactive hilar neurons, particularly in caudal dentate regions, were lost 3-5 weeks after kainic acid treatment. Our findings suggest that alpha8beta1 may mediate adhesive interactions of the dendritic processes of mossy cells and somatostatin-containing hilar neurons with other cellular elements or with extracellular matrix components. They also suggest that alpha8 may be susceptible to activity-dependent proteolysis that could modulate its function in the somatodendritic compartment of these cells.

Osteopontin deficiency in rat vascular smooth muscle cells is associated with an inability to adhere to collagen and increased apoptosis.

Osteopontin (OPN) is an extracellular matrix protein that has been implicated in vascular smooth muscle cell (VSMC) adhesion. We have previously described the generation of OPN-deficient VSMC that displayed altered adhesion to collagen. We have examined further the causes and consequences of this altered adhesion. OPN-deficiency was associated with a significant reduction in surface expression of alpha1 and beta1 integrins (mean fluorescence intensity alpha1: OPN-deficient 0.135+/-0.04 vs. control 0.313+/-0.05, p < 0.0001; beta1: OPN-deficient 0.398+/-0.09 vs. control 0.570+/-0.05, p < 0.004). Treatment of normal VSMC with antibody to alpha1 recapitulated the adhesion defect. OPN-deficient cells without collagen exposure had an apoptotic fraction of 1.9%, which increased to 95.7% after 24 hours exposure to collagen. Exogenous OPN added to cultures within 15 minutes of plating restored normal cell adhesion, but did not prevent cells from undergoing apoptosis. Normal VSMC had no detectable apoptosis after 24 hours incubation in suspension, whereas OPN-deficient cells had an apoptotic fraction of 37.5% when incubated in suspension under the same conditions. The data suggest that OPN-deficient VSMC have two distinct abnormalities: an alpha1beta1-mediated inability to adhere normally to collagen and an increased propensity for apoptosis.

Making memories stick: cell-adhesion molecules in synaptic plasticity.

Synapses are adhesive junctions highly specialized for interneuronal signalling in the central nervous system. The strength of the synaptic signal can be modified (synaptic plasticity), a key feature of the cellular changes thought to underlie learning and memory. Cell-adhesion molecules are important constituents of synapses, with well-recognized roles in building and maintaining synaptic structure during brain development. However, growing evidence indicates that cell-adhesion molecules also play important and diverse roles in regulating synaptic plasticity and learning and memory. This review focuses on recent advances in understanding the molecular mechanisms through which adhesion molecules might regulate synaptic plasticity.

Release of active tissue factor by human arterial smooth muscle cells.

Tissue factor (TF), the initiator of coagulation, is thought to function predominantly at the cell surface. Recent data have suggested that active TF is present extracellularly in atherosclerotic plaques, the arterial wall, and the blood. This study was conducted to determine whether smooth muscle cells (SMCs), a major source of arterial TF, could generate extracellular TF. Active TF accumulated in the medium of cultured human SMCs, representing approximately 10% of that measured in the underlying cells at 24 hours. Platelet-derived growth factor, phorbol ester, and tumor necrosis factor-alpha caused approximately 3-fold increases in TF activity in the medium. Release of TF into the medium was dependent on the presence of the TF transmembrane domain but not the cytoplasmic domain. Antibodies to TF precipitated most of the activity from the culture medium, whereas antibodies to the beta(1)-integrin subunit precipitated approximately 33% of the activity. Treatment with detergent or phosphatidylserine:phosphatidylcholine did not increase activity, suggesting that all TF released by SMCs was in the appropriate lipid milieu and not encrypted. Western blotting showed that the medium contained full-length TF protein. Fluorescent cytometry showed that extracellular TF was present largely in particles < or =200 nm, which had a density of 1.10 g/mL. We hypothesize that active extracellular TF found in the injured arterial wall and atherosclerotic plaques derives, in part, from SMC microparticles.

Expression of the integrin alpha8beta1 during pulmonary and hepatic fibrosis.

The fibrotic response after diverse forms of injury is characterized by the accumulation of extracellular matrix proteins, proliferation of myofibroblast-like cells, and organ contraction. Myofibroblasts are key effector cells in the development of the fibrotic response. They contribute to fibrosis through both increased cell number (proliferation) and enhanced matrix synthesis. Integrins, a class of cell adhesion molecules, are mediators of cell-extracellular matrix protein interactions that are important in the proliferative and migratory response of cells to matrix proteins. We have previously cloned the human integrin subunit alpha8, documented its high expression in lung tissue, and established it as a receptor for the matrix proteins fibronectin, vitronectin, and tenascin. We now demonstrate that alveolar interstitial cells are the primary cell type expressing alpha8beta1 in the lung parenchyma. Expression of alpha8beta1 is concentrated primarily along the thinned extensions of cells and at the tips of filopodia. Because of its unique distribution in alveolar interstitial cells, we hypothesized that it may play a role in the fibrotic response after injury. In bleomycin-induced pulmonary fibrosis, there is increased expression of alpha8beta1 by interstitial fibroblasts, the majority of which coexpress alpha smooth muscle actin, a marker of tissue myofibroblasts. To establish a more general role for alpha8beta1 during organ fibrosis, we further examined its expression in two rat models of liver fibrosis. During hepatic injury due to either carbon tetrachloride injury or bile duct ligation, we demonstrate de novo expression of alpha8beta1 in activated hepatic stellate cells, the myofibroblast equivalent in liver. Taken together, the data localize alpha8beta1 to myofibroblast-like cells during wound healing and suggest that signal transduction through the alpha8beta1 integrin may contribute to the fibrotic response of organs to injury.

Attachment of primary neonatal rat astrocytes to vitronectin is mediated by integrins alphavbeta5 and alpha8beta1: modulation by the type 1 plasminogen activator inhibitor.

Vitronectin is expressed in a cell-specific manner in the developing brain and concentrated in the brain during disease processes, such as germinal matrix hemorrhage and infarction, in which there is breakdown of the blood-brain barrier. In this study, we identified the integrin receptors that mediate attachment of primary neonatal rat astrocytes to vitronectin. Using fluorescent activated cell sorter and immunoprecipitation analyses, we established that the vitronectin receptor integrins alphavbeta5 and alpha8beta1, but not alphavbeta3, are expressed on neonatal rat astrocytes. Attachment of the neonatal astrocytes to vitronectin was inhibited (85%) in an additive manner by neutralizing anti-alphavbeta5 and anti-beta1 antibodies. Attachment to vitronectin was also inhibited in a dose-dependent manner by the type I plasminogen activator inhibitor (PAI-1), a serine protease inhibitor. Our data demonstrate that unstimulated primary neonatal rat astrocytes attach to vitronectin, utilizing integrins alphavbeta5 and alpha8beta1, and that this attachment is regulated by PAI-1.

Superfibronectin, a multimeric form of fibronectin, increases HIV infection of primary CD4+ T lymphocytes.

The ability of viruses and bacteria to interact with the extracellular matrix plays an important role in their infectivity and pathogenicity. Fibronectin is a major component of the extracellular matrix in lymph node tissue, the main site of HIV deposition and replication during the chronic phase of infection. Therefore, we asked whether matrix fibronectin (FN) could affect the ability of HIV to infect lymphocytes. To study the role of matrix FN on HIV infection, we used superfibronectin (sFN), a multimeric form of FN that closely resembles in vivo matrix FN. In this study we show that HIV-1IIIB efficiently binds to multimeric fibronectin (sFN) and that HIV infection of primary CD4+ lymphocytes is enhanced by >1 order of magnitude in the presence of sFN. This increase appears to be due to increased adhesion of viral particles to the cell surface in the presence of sFN, followed by internalization of virus. Enzymatic removal of cell surface proteoglycans inhibited the adhesion of HIV-1IIIB/sFN complexes to lymphocytes. In contrast, Abs to integrins had no effect on binding of HIV-1IIIB/sFN complexes to lymphocytes. The III1-C peptide alone also bound HIV-1IIIB efficiently and enhanced HIV infection, although not as effectively as sFN. HIV-1IIIB gp120 envelope protein binds to the III1-C region of sFN and may be important in the interaction of virus with matrix FN. We conclude that HIV-1IIIB specifically interacts with the III1-C region within matrix FN, and that this interaction may play a role in facilitating HIV infection in vivo, particularly in lymph node tissue.

WT1 expression induces features of renal epithelial differentiation in mesenchymal fibroblasts.

The WT1 tumor suppressor gene, implicated in hereditofamilial and sporadic Wilms' tumor, is required for normal renal development and is up-regulated during the mesenchymal-epithelial transition. NIH3T3 fibroblasts overexpressing WT1 were less proliferative, larger in size and more firmly attached to tissue culture plastic, suggesting an alteration of their state of differentiation. These cells were studied in vivo by subcutaneous injection into nude mice. The resulting tumors exhibited epithelioid histopathology and formed desmosome-like structures. Molecular analyses of these WT1 expressing fibroblasts grown in culture and in nude mice revealed significant alterations in the expression of many kidney epithelial markers. These studies indicate that WT1 expression can initiate features of a program of epithelial differentiation consistent with a prominent role for WT1 in the mesenchymal epithelial transition that occurs during renal development. Through this work we identified a number of novel target genes for the WT1 transcription factor, including uvomorulin, integrin alpha8 and perlecan, and suggest that WTI may activate the IGF-II gene, also implicated in the development of Wilms' tumor.

Integrins inhibit angiotensin II-induced contraction in rat aortic rings.

Many extracellular matrix proteins contain the tripeptide sequence arginine-glycine-aspartate (RGD). This RGD motif is recognized by integrins, a family of adhesion receptors present on vascular smooth muscle cells. In the present study, we examined the ability of different RGD-containing peptides to affect the contraction of rat aortic rings in response to different agonists. We found that the peptide RGDS inhibited angiotensin-induced contraction in a dose dependent manner. In contrast, the peptides RGDW and RGES had no effect on angiotensin-induced contractility. We show that function-blocking antibodies to the integrins alphavbeta3 and alpha5beta1 also inhibit angiotensin-induced contraction. These effects were observed in the absence of an intact endothelium. In contrast, neither an antibody directed against the beta1 subunit nor the peptide RGDS had an effect on phenylephrine or 5-hydroxytryptamine-induced contraction. These data suggest that interactions of vascular smooth muscle with components of the surrounding extracellular matrix may influence the response of smooth muscle to agonists.

Elmer's glue, Elsie and you: clinical applications of adhesion molecules.

An effective response to injury or inflammation requires leukocyte migration from the endovascular compartment into areas of inflammation. This process requires the appropriate expression of adhesion molecules, which mediate cell-cell and cell-extracellular matrix interactions. A better understanding of the roles of adhesion molecules in normal and pathological conditions might lead to the development of more effective therapeutic interventions. Features of several classes of adhesion molecules, including immunoglobulin superfamily, selectins, and integrins, are reviewed along with how they participate in leukocyte-endothelial interactions. The role of cell adhesion molecules in a variety of pathological conditions, including graft rejection, reperfusion injury, and acute lung injury are discussed. In addition, some recent studies that explore therapeutic uses of adhesion molecules are summarized.

Changes in endothelial cell and smooth muscle cell integrin expression during closure of the ductus arteriosus: an immunohistochemical comparison of the fetal, preterm newborn, and full-term newborn rhesus monkey ductus.

Anatomical closure of the ductus arteriosus requires normally quiescent luminal endothelial cells and medial smooth muscle cells to migrate into the subendothelial space forming intimal mounds that eventually coalesce and occlude the vessel's lumen. The migration of endothelial cells and smooth muscle cells requires the presence of integrin receptors that interact with the surrounding matrix. We used immunohistochemical staining to examine the repertoires of integrins expressed by endothelial cells and smooth muscle cells during postnatal closure of the ductus arteriosus in full-term and preterm rhesus monkeys. In the fetal ductus, luminal endothelial cells have a limited repertoire of integrins. During postnatal ductus closure, luminal endothelial cells, of both term and preterm monkeys, change their phenotype and express the full repertoire of integrins found on growing capillary endothelial cells (alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 6 beta 1, alpha v beta 1, alpha 6 beta 4, and alpha v beta 5). Similarly, during ductus closure, smooth muscle cells of both term and preterm monkeys expand their integrin repertoire to include the alpha 5 beta 1 and alpha v beta 3 integrins; these two integrins have been shown to be essential for smooth muscle cell migration in vitro. These changes in integrin profile occur at the same time the endothelial and smooth muscle cells invade their neighboring compartments. In contrast, preterm monkeys with a persistently patent ductus lumen fail to develop these changes in integrin expression and fail to develop neointimal mounds. No evidence of intimal thickening occurs in the absence of changes in integrin expression. Therefore, endothelial cells and smooth muscle cells change phenotypes to produce the intimal thickening required for ductus closure.

Regional and ultrastructural distribution of the alpha 8 integrin subunit in developing and adult rat brain suggests a role in synaptic function.

Integrins are heterodimeric cell adhesion molecules comprised of alpha and beta subunits that have been implicated in the regulation of neuronal migration, differentiation, and process outgrowth. They mediate both cell-extracellular matrix and cell-cell interactions. The integrin alpha 8 beta 1 is a receptor for fibronectin, tenascin, and vitronectin that has been localized to axonal tracts and several types of non-neuronal cells in chick embryos and to smooth muscle cells in adult mammalian tissues. In this report, we describe the distribution of the alpha 8 subunit in the developing and adult mammalian brain. By light microscopy, alpha 8 labeling in the rat brain was found predominantly in neurons. It was primarily localized within perikarya and dendrites, but was also observed in certain fiber tracts. alpha 8 immunoreactivity was most concentrated in the olfactory bulb, hippocampal formation, substantia nigra, ventral tegmental area, and superior olivary complex, but was also found at moderate levels in several regions including layer 5 of the cerebral cortex. alpha 8 labeling was detected as early as E16, peaked in most areas during the first 3 postnatal weeks, and persisted in the adult. Electron microscopic analysis of the adult hippocampal formation revealed a striking concentration of alpha 8 immunoreactivity in the spines and postsynaptic densities of dendrites. These results suggest that alpha 8 is involved in the regulation of axonal and dendritic growth of some neurons in the developing central nervous system (CNS) and provide ultrastructural evidence that integrins may participate in the formation, maintenance, or plasticity of synapses.

Presentation of AIDS-related pulmonary Kaposi's sarcoma diagnosed by bronchoscopy.

Kaposi's sarcoma (KS) is the most common neoplasm in persons infected with the human immunodeficiency virus (HIV). However, information about the presenting features of pulmonary KS is limited. To describe the clinical, laboratory, and radiographic features of pulmonary KS, medical records and chest radiographs of 168 patients with pulmonary KS diagnosed by bronchoscopy during a 7-yr period were reviewed. All of the patients were HIV-seropositive males, of whom 95% identified homosexual or bisexual sex as a risk factor for HIV infection. The median CD4 lymphocyte count was 19 cells/microliter. The most common symptoms were cough, dyspnea, and fever. Patients with a concurrent opportunistic pneumonia had a higher median serum lactate dehydrogenase (LDH) concentration than did those with pulmonary KS alone (p<0.001). The most common chest radiograph findings were bronchial-wall thickening, nodules, Kerley B lines, and pleural effusions. The presence of granular opacities or cystic spaces usually indicated concomitant Pneumocystitis carinii pneumonia (p < 0.001). Twenty-six patients (15.5%, 95% CI = 10.2% to 20.8%) had pulmonary KS in the absence of mucocutaneous involvement. The presentation of pulmonary KS is characterized by symptoms that cannot be distinguished from those of a superimposed infection. An elevated serum LDH concentration or a chest radiograph with granular opacities or cystic spaces should raise the suspicion of concurrent opportunistic pneumonia. The diagnosis of pulmonary KS should be considered in an HIV-infected homosexual or bisexual male with respiratory symptoms even in the absence of mucocutaneous lesions.

The human integrin alpha 8 beta 1 functions as a receptor for tenascin, fibronectin, and vitronectin.

The integrin family of adhesion receptors consists of at least 21 heterodimeric transmembrane proteins that differ in their tissue distribution and ligand specificity. The recently identified alpha 8 integrin subunit associates with beta 1 and is predominantly expressed in smooth muscle and other contractile cells in adult tissues, and in mesenchymal and neural cells during development. We now show that alpha 8 beta 1 specifically localizes to focal contacts in cells plated on the extracellular matrix proteins fibronectin or vitronectin. In addition we show that human embryonic kidney cells (293), transfected with alpha 8 cDNA, express alpha 8 beta 1 on their surface and use this receptor for adhesion to fibronectin and vitronectin. Furthermore, alpha 8 beta 1 binds to both fibronectin- and vitronectin-Sepharose and can be specifically eluted from either matrix protein by the arginine-glycine-aspartic acid (RGD)-containing peptide, GRGDSP. Because fibronectin and vitronectin adhesion appeared to be mediated by RGD, we examined additional RGD-containing proteins, including tenascin, fibrinogen, thrombospondin, osteopontin, and denatured collagen type I. We found that only tenascin was able to mediate adhesion of alpha 8-transfected 293 cells. By using recombinant fragments of tenascin in adhesion assays, we were able to localize the alpha 8 beta 1 binding domain of tenascin to the RGD-containing third fibronectin type III repeat. These data strongly suggest that tenascin, fibronectin, and vitronectin are ligands for alpha 8 beta 1 and that this integrin binds to the RGD site in each of these ligands through mechanisms that are distinct and separate from alpha 5- and alpha v-containing integrins.

Frequency and importance of barotrauma in 100 patients with acute lung injury.

OBJECTIVES: To determine the occurrence rate of barotrauma in acute lung injury patients, whether barotrauma is an independent risk factor for mortality, and the role of barotrauma in the outcome of those patients who died. DESIGN: Prospective, cohort study. SETTING: Intensive care units at a university hospital. PATIENTS: Consecutive adult patients (n = 100) meeting the usual criteria for a diagnosis of acute lung injury requiring mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: Barotrauma occurred in 13 (13%) of 100 patients. Mortality rates were not different in patients with (76%) and without (64%) barotrauma. Using univariate analysis, barotrauma was not associated with increased mortality (odds ratio 1.85; confidence interval 0.42 to 9.20; p = .53). However, when barotrauma was incorporated into a logistic regression model, along with other potential predictors of mortality, barotrauma was associated with increased mortality (odds ratio 6.15; confidence interval 1.11 to 33.9; p = .017). The presence of nonpulmonary organ dysfunction and sepsis was strongly associated with mortality. In the setting of barotrauma, the mortality rate was 100% if associated with two or more nonpulmonary organ dysfunctions compared with a mortality rate of 40% with one or no nonpulmonary organ failure. Barotrauma contributed directly to the cause of death in only one patient. CONCLUSIONS: Barotrauma occurred in only 13% of patients with acute lung injury. Barotrauma was an independent marker of mortality when adjusted for other predictors of mortality. However, barotrauma directly contributed to < 2% of all deaths. We hypothesize that barotrauma is an indication of severity of acute lung injury rather than a major cause of increased mortality.

Sequence and tissue distribution of the human integrin alpha 8 subunit: a beta 1-associated alpha subunit expressed in smooth muscle cells.

Integrins are a major family of cell adhesion molecules involved in cell-cell and cell-extracellular matrix interactions. Each integrin is a heterodimeric glycoprotein composed of an alpha and a beta subunit. We now report the cDNA sequence and distribution of a new human integrin alpha subunit. This sequence is 78% identical to the previously reported chicken alpha 8 integrin sequence. Thus, we have designated this subunit as human alpha 8. By northern blot analysis, an alpha 8 probe detects two mRNA species of approximately 6.5 and 4.0 kb in neuroglioma H4 cells. An anti-alpha 8 polyclonal antibody precipitates a protein complex containing the beta 1 subunit associated with the putative alpha 8 subunit, which has an apparent molecular mass of 180 kDa (non-reduced) or 155 kDa and 25 kDa (reduced). Immunohistochemistry with anti-alpha 8 polyclonal antibody in adult rat tissues shows prominent staining in vascular and visceral smooth muscle. In addition, the antibody strongly stained kidney mesangial cells and a cell type in the alveolar wall of the lungs, most likely corresponding to alveolar myofibroblasts. These results suggest that in adult mammalian tissues, alpha 8 is predominantly expressed in smooth muscle and smooth muscle-like contractile cells.

Diagnosis of Pneumocystis carinii infection in HIV-seropositive patients by identification of P carinii in pleural fluid.

Pneumocystis carinii pneumonia (PCP) is the most common pulmonary complication of AIDS and is typically diagnosed by the identification of P carinii organisms in sputum, bronchoalveolar lavage fluid, or tissue obtained with transbronchial biopsy. We describe two HIV-seropositive patients with pleural effusions in whom the diagnosis of P carinii infection was made by examination of pleural fluid. Pleural effusions associated with PCP are very unusual but can provide a source of diagnostic material particularly in those HIV patients who have development of a spontaneous pneumothorax and require chest tube insertion.

Effect of aerosolized pentamidine prophylaxis on the clinical severity and diagnosis of Pneumocystis carinii pneumonia.

To determine if the use of aerosolized pentamidine prophylaxis decreases the clinical severity or the sensitivity of diagnostic tests for Pneumocystis carinii pneumonia (PCP), we conducted a retrospective matched cohort comparison study of patients admitted to San Francisco General Hospital with PCP from August 1, 1989, to June 30, 1990. Patients who had received pentamidine prophylaxis during at least the 2 months prior to the diagnosis of PCP were matched with patients who had not received the drug. Matching was based on the number of prior episodes of PCP, sex, age, and risk factors for human immunodeficiency virus infection. As markers of clinical severity, we chose alveolar-arterial oxygen difference, serum lactate dehydrogenase levels, outpatient versus inpatient treatment, length of hospitalization, length of intravenous anti-pneumocystis treatment, development of respiratory failure, in-hospital mortality, and chest radiographic appearance. Although, of the 27 matched pairs identified, significantly fewer of the pentamidine cohort were treated as inpatients, and significantly more of this cohort had upper lobe dominant disease on chest radiograph, we found no other significant differences between markers of clinical severity for the two cohorts. In addition, we found no significant differences in the rate of sputum or bronchoalveolar lavage positivity for P. carinii between the two cohorts. We conclude that, although hospitalization is less common in patients with a history of prophylactic pentamidine use, aerosolized pentamidine prophylaxis does not decrease the clinical severity or the sensitivities of sputum induction or bronchoalveolar lavage as diagnostic tests for PCP.