Caspase-independent apoptosis in infected macrophages triggered by sulforaphane via Nrf2/p38 signaling pathways.

Mycobacterium abscessus (Mabs), a non-tuberculous mycobacterium, is an emerging and rapidly growing opportunistic pathogen that is frequently found in patients with cystic fibrosis and in immunosuppressed patients. Its high tolerance to antibiotics is of great concern for public health. In this study, our results showed that human THP-1-derived macrophages infected with M. abscessus presented an increase in ROS production and cell necrosis. In addition, M. abscessus infection triggered activation of the Nuclear factor E2-related factor 2 (Nrf2) signaling pathway, and the induction of HO-1 and NQO1 expression levels. Interestingly, pretreatment of macrophages with sulforaphane (SFN), an activator of the antioxidant key regulator Nrf2, followed by M. abscessus infection significantly decreased mycobacterial burden. We demonstrated that this reduction in mycobacterial growth was due to an activation in cell apoptosis in SFN-pretreated and M. abscessus-infected macrophages. Pretreatment with specific MAPK inhibitors, PD98059, SP600125, and SB203580 to ERK, JNK, and p38 respectively, failed to inhibit induction of Nrf2 expression, suggesting that Nrf2 signaling pathway was upstream of MAPK signaling. Activation of cell apoptosis was caspase 3/7 independent but p38 MAPK dependent. Moreover, p38 MAPK induction was abolished in macrophages transfected with Nrf2 siRNA. In addition, p38 inhibitor abolished Nrf2-dependent apoptosis in infected macrophages. Taken together, our results indicate that modulation of the Nrf2 signaling using Nrf2 activators may help potentiate the actual drug therapies used to treat mycobacterial infection.

Regulation of oxidative stress by Nrf2 in the pathophysiology of infectious diseases.

The innate immune system, including phagocytic cells, is the first line of defense against pathogens. During infection by microorganisms such as viruses, bacteria, or parasites, phagocytic cells produce an excess of oxidants, a crucial process for the clearance of pathogens. This increase in oxidants creates an imbalance between oxidants and endogenous antioxidants. Left unchecked, this acute or chronic oxidative stress can lead to apoptotic cell-death and oxidative stress-induced diseases including neurodegenerative and cardiovascular disorders, premature aging, secondary infections, and cancer. The activation of nuclear factor E2-related factor 2 (Nrf2) is an efficient antioxidant defensive mechanism used by host cells to counteract oxidative stress. The transcription factor Nrf2 has been identified as the master regulator of several hundred of genes involved in the antioxidant defense response. The review objectives were to collect recent findings on the contribution of oxidative stress to complications of infection, and to highlight the beneficial impact of antioxidants in reducing inflammation and oxidant-related tissue damage. Furthermore, a direct relationship between infection and decline in Nrf2 activity has been demonstrated. Thus, an interesting therapeutic approach in disease prevention and treatment of stress-related diseases may consist in optimizing antibiotic or antiviral therapy with a combination of Nrf2 inducer treatment.

NRF2 targeting: a promising therapeutic strategy in chronic obstructive pulmonary disease.

Several convergent destructive mechanisms such as oxidative stress, alveolar cell apoptosis, extracellular matrix proteolysis and chronic inflammation contribute to chronic obstructive pulmonary disease (COPD) development. Evidence suggests that oxidative stress contributes to the pathophysiology of COPD, particularly during exacerbations. Nuclear factor erythroid-2-related factor 2 (NRF2), a transcription factor expressed predominantly in epithelium and alveolar macrophages, has an essential protective role in the lungs through the activation of antioxidant response element-regulated antioxidant and cytoprotective genes. Animal models and human studies have identified NRF2 and several NRF2 target genes as a protective system against inflammation and oxidative stress from cigarette smoke, a major causative factor in COPD development. Hence, NRF2 targeting might provide clinical benefit by reducing both oxidative stress and inflammation in COPD.

Oxidative stress targets in pulmonary emphysema: focus on the Nrf2 pathway.

IMPORTANCE OF THE FIELD: Oxidative stress has been implicated in the pathogenesis of pulmonary emphysema. Nuclear factor erythroid-2-related factor 2 (Nrf2) a major antioxidant transcription factor could play a protective role in pulmonary emphysema. AREAS COVERED IN THIS REVIEW: Nrf2 is ubiquitously expressed throughout the lung, but is predominantly found in epithelium and alveolar macrophages. Evidence suggests that Nrf2 and several Nrf2 downstream genes have an essential protective role in the lung against oxidative stress from environmental pollutants and toxicants such as cigarette smoke, a major causative factor for the development and progression of pulmonary emphysema. Application of Nrf2-deficient mice identified an extensive range of protective roles for Nrf2 against the pathogenesis of pulmonary emphysema. Therefore, Nrf2 promises to be an attractive therapeutic target for intervention and prevention strategies. WHAT THE READER WILL GAIN: In this review, we discuss recent findings on the association of oxidative stress with pulmonary emphysema. We also address the mechanisms of Nrf2 lung protection against oxidative stress based on emerging evidence from experimental oxidative disease models and human studie. TAKE HOME MESSAGE: The current literature suggests that among oxidative stress targets, Nrf2 is a valuable therapeutic target in pulmonary emphysema.

Prolonged cigarette smoke exposure decreases heme oxygenase-1 and alters Nrf2 and Bach1 expression in human macrophages: roles of the MAP kinases ERK(1/2) and JNK.

Tobacco may be involved in the decreased macrophage heme oxygenase-1 (HO-1) expression described in smoking-induced severe emphysema, via the nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1)-BTB and CNC homology 1, basic leucine zipper transcription factor 1 (Bach1) pathway. We assessed in vitro effects of cigarette smoke condensate (CS) in the human monocyte/macrophage cell line (THP-1). CS exposure led to increased HO-1 and nuclear Nrf2 expression (6 h) followed by decreased HO-1 expression concomitantly with nuclear Nrf2/Bach1 ratio decrease (72h). CS-induced mitogen-activated protein kinase (MAPK) phosphorylation. Extracellular-signal-regulated kinase(1/2) (ERK(1/2)) and c-Jun NH2-terminal kinase (JNK) inhibition completely abrogated CS effects on HO-1 expression and nuclear Nrf2/Bach1 translocation. These results suggest that ERK(1/2) and JNK are involved in CS-induced biphasic HO-1 expression by a specific regulation of Nrf2/Keap1-Bach1.

Altered Nrf2/Keap1-Bach1 equilibrium in pulmonary emphysema.

BACKGROUND: Oxidative stress, resulting from the increased oxidative burden and decreased level of antioxidant proteins, plays a role in the pathophysiology of smoking-related pulmonary emphysema. Expression of several antioxidant proteins, such as heme oxygenase-1 (HO-1), glutathione peroxidase 2 (GPX2) and NAD(P)H:quinone oxidoreductase 1 (NQO1), results from an equilibrium created by positive or negative regulation by the transcription factors Nrf2, Keap1 and Bach1, respectively. However, whether the expression of these transcription factors is altered in emphysema and could account for decreased expression of antioxidant proteins is not known. A study was undertaken to investigate the expression and subcellular localisation of Nrf2, Keap1 and Bach1 as potential regulators of HO-1, GPX2 and NQO1 in alveolar macrophages, a key cell in oxidative stress, in lung surgical specimens from non-smokers without emphysema and smokers with and without emphysema. METHODS AND RESULTS: Western blot, immunohistochemical and laser scanning confocal analysis revealed that the Nrf2 protein level decreased significantly in whole lung tissue and alveolar macrophages (cytosol and nucleus) in patients with emphysema compared with those without emphysema. Conversely, Bach1 and Keap1 levels were increased in patients with emphysema. These modifications were associated with a parallel decrease in the expression of HO-1, GPX2 and NQO1 at the cellular level, which was inversely correlated with airway obstruction and distension indexes, and increased macrophage expression of the lipid peroxidation product 4-hydroxy-2-nonenal. Silencing RNA experiments in vitro in THP-1 cells were performed to confirm the cause-effect relation between the loss of Nrf2 and the decrease in HO-1, NQO1 and GPX2 expression. Nrf2/Keap1-Bach1 equilibrium was altered in alveolar macrophages in pulmonary emphysema, which points to a decreased stress response phenotype. CONCLUSIONS: This finding opens a new view of the pathophysiology of emphysema and could provide the basis for new therapeutic approaches based on preservation and/or restoration of such equilibrium.

[Respiratory manifestations during the course of Sjogren's syndrome]. / Manifestations respiratoires au cours du syndrome de Gougerot-Sjögren.

INTRODUCTION: Sjogren's syndrome is a common auto-immune disease. BACKGROUND: Clinically significant pulmonary involvement affects approximately 10% of patients and may be the first manifestation of the disease, putting the respiratory physician in a position to suspect and confirm the diagnosis. Besides interstitial lung disease and bronchial disorders, cough is a common symptom of the disease and particularly difficult to treat. Lung cysts and amyloid deposits, sometimes associated with lymphoma, have recently been described. The development of a primary pulmonary lymphoma, usually from MALT, is a major complication of the disease. VIEWPOINT: Characterisation of the pathophysiology of pulmonary involvement in Sjogren's syndrome and the institution of specific treatment merits the interest of the respiratory physician. CONCLUSION: The respiratory physician should consider the diagnosis of Sjogren's syndrome in many different clinico-pathological situations.

Assessment of the cough reflex after propofol anaesthesia for colonoscopy.

BACKGROUND: Dysfunction of the cough reflex as a result of the lingering effects of anaesthetics may lead to aspiration pneumonia or retained secretions after general anaesthesia. It is unknown whether low concentrations of propofol alter the cough reflex in the early period after anaesthesia. The objective of this study was to investigate the effect of low concentrations of propofol on the cough reflex sensitivity as assessed by the cough reflex threshold to an inhaled irritant. METHODS: Fifteen, ASA I-II, non-smoking patients undergoing elective colonoscopy were studied. Anaesthesia was induced and maintained with a blood target-controlled propofol infusion. Cough reflex threshold was measured with citric acid. Increasing concentrations of nebulized citric acid (2.5, 5, 10, 20, 40, 80, 160, 320, and 640 mg ml(-1)) were delivered during inspiration until a cough was evoked. The citric acid concentration eliciting one cough (C1) was defined as the cough reflex threshold. C1 was log transformed for statistical analysis (Log C1). Log C1 was measured before anaesthesia and during the recovery period with estimated decreasing propofol concentrations of 1.2, 0.9, 0.6, and 0.3 microg ml(-1). RESULTS: Log C1 (median; interquartile range) measured with propofol concentrations of 1.2, 0.9, 0.6, 0.3, and 0 microg ml(-1) were 1.9 (0.6), 1.9 (1.0), 1.9 (1.1), 1.9 (0.6), and 1.9 (0.7) mg ml(-1) (NS), respectively. However, light sedation was observed with propofol concentrations of 1.2 and 0.9 microg ml(-1). CONCLUSION: This study indicates that residual sedation after propofol anaesthesia for colonoscopy does not adversely affect the cough reflex.

Culture at high density improves the ability of human macrophages to control mycobacterial growth.

The mechanisms through which granuloma formation helps control mycobacterial infection are poorly understood, but it is possible that the accumulation of macrophages at high density at sites of infection promotes the differentiation of macrophages into cells with improved mycobactericidal activity. To test this possibility, varying numbers of monocytes were cultured in 96-well plates for 3 days, infected with Mycobacterium bovis bacillus Calmette-Guérin, and mycobacterial number was assessed 7 days after infection based on the measurement of luciferase activity expressed by a mycobacterial reporter strain or by counting CFU. Mycobacterial growth was optimal in cultures containing 5 x 10(4) cells/well, but increasing the number of cells to 2 x 10(5) cells/well resulted in complete inhibition of mycobacterial growth. This effect could not be explained by differences in mycobacterial uptake, multiplicity of infection, acidification of the extracellular medium in high density cultures, enhanced NO production, or paracrine stimulation resulting from secretion of cytokines or other proteins. The morphology of cells cultured at high density was strikingly different from that of monocytes cultured at 5 x 10(4) cells/well, including the appearance of numerous giant cells. The bacteriostatic activity of monocyte-derived macrophages was also dependent on cell number, but fewer of these more mature cells were required to control mycobacterial growth. Thus, the ability of human macrophages to control mycobacterial infection in vitro is influenced by the density of cells present, findings that may help explain why the formation of granulomas in vivo appears to be a key event in the control of mycobacterial infections.

Effect of stimulation of human macrophages on intracellular survival of Mycobacterium bovis Bacillus Calmette-Guerin. Evaluation with a mycobacterial reporter strain.

The mechanisms through which immune and inflammatory responses stimulate the expression of antimycobacterial activity by human macrophages remain poorly defined. To study this question, we developed a method permitting the rapid quantification of viable mycobacteria, based on the detection of luciferase activity expressed by a Mycobacterium bovis Bacillus Calmette-Guerin (BCG) reporter strain, and used this approach to evaluate mycobacterial survival in human monocyte-derived macrophages following stimulation with cytokines and through crosslinking of costimulatory molecules expressed on the cell surface. Modest proliferation, followed by persistence of mycobacteria, was observed in unpretreated macrophages as assessed both by measurement of luciferase activity and by the evaluation of colony forming units. Of the 19 cytokines tested, only granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) were found to improve the mycobactericidal activity of monocyte-derived macrophages. In both cases, this effect was observed only when macrophages were pretreated with the cytokines prior to infection. In contrast, pretreatment of human macrophages with interferon-gamma, either alone or in combination with other mediators (including tumor necrosis factor-alpha and 1,25[OH]2-vitamin D3), did not improve mycobacterial killing. The stimulation of macrophages through several different costimulatory molecules known to participate in macrophage-lymphocyte interactions (CD4, CD40, CD45, CD86, CD95 [Fas/Apo-1]) also failed to improve mycobactericidal activity. This study shows that GM-CSF and IL-3, cytokines whose receptors are known to share a common subunit and to use common second messengers, may contribute to the stimulation of mycobactericidal activity in humans. The ability to rapidly screen the effects of different macrophage stimuli on mycobacterial survival through the detection of luciferase activity should help define additional signals required for optimal antimycobacterial responses.

Langerhans cells in Langerhans cell granulomatosis are not actively proliferating cells.

Pulmonary Langerhans cell granulomatosis (LCG), also called histiocytosis X, is a disorder of unknown etiology characterized by the presence of destructive granulomas containing numerous Langerhans cells (LCs). The process may be localized or multifocal, and it remains unclear whether the same pathogenic mechanism is involved in all forms of the disease. It is often assumed that the massive accumulation of LCs at the sites of the lesions results from the abnormal proliferation of these cells, although it has been suggested that LCG in adults, at least in the lung, could be a reactive disorder initiated by activated LCs. Little is known, however, concerning the mechanisms responsible for the accumulation of large numbers of LCs in the course of the disease, and the relative contribution of recruitment and local proliferation of these cells remains to be established. To investigate this question, the proportion of replicating LCs was evaluated in biopsied granulomas from patients with localized or diffuse form of LCG by means of several histopathological techniques currently used in assessment of cell proliferation. The findings demonstrate that, except for proliferating cell nuclear antigen (PCNA), all parameters measured are low in all forms of the disease. They are similar to those of renewing epithelial cells and clearly less than those of neoplastic cells. These data strongly suggest that LCs in LCG granulomas are not a rapidly dividing cell population and that local LC replication makes only a minimal contribution to granuloma maintenance. Caution appears to be necessary in the use of PCNA as a marker of growth fraction.

Cytokine patterns in tuberculous and sarcoid granulomas: correlations with histopathologic features of the granulomatous response.

Cytokines play an important role in granuloma formation, but the extent that cytokine profiles are similar in different granulomatous diseases and whether differences in the histopathologic features of the granulomatous response results from differences in cytokine production have not been evaluated. To investigate these questions, we used RT-PCR to quantify the expression of mRNAs coding for 16 cytokines in granulomatous lymph nodes from patients with tuberculosis and sarcoidosis and from control tissues, and we sought correlations between the level of expression of these cytokines and the histopathologic features of the granulomas. Expression of mRNAs coding for a number of cytokines (IL-1beta, IFN-gamma, TNF-alpha, granulocyte-macrophage (GM)-CSF, IL-12 (p40), and lymphotoxin-beta) was increased in tuberculous and sarcoid granulomas compared with that of control tissues. All sarcoid granulomas were shown to express a Th1 pattern of cytokine mRNAs, while tuberculous lymph nodes expressed either a Th1 or a Th0 profile. GM-CSF and lymphotoxin-beta mRNAs were more abundant in sarcoid than in tuberculous granulomas, whereas IL-8 mRNA was strongly expressed only in tuberculous lymph nodes. Strong expression of GM-CSF, TNF-alpha, and IL-8 by granulomas was shown to be correlated, respectively, with the presence of florid granulomatous lesions, the absence of central necrosis, and the presence of neutrophil infiltration. These results demonstrate that the formation of tuberculous and sarcoid granulomas in humans is associated with the expression of characteristic cytokine profiles and indicate that the expression of certain cytokines is associated with the development of specific pathologic features in the resulting granulomas.

Activation of T-cells through an antigen-independent alternative pathway induces precocious sensitivity to Fas-induced apoptosis.

Autoreactive T-cells can be activated inadvertently during immune responses through antigen-independent pathways. It has been suggested that Fas/Fas ligand interactions may play a role in eliminating these cells, but the extent that cells activated through such alternative pathways are sensitive to Fas-induced apoptosis has not been extensively evaluated. Proliferation of peripheral blood T-cells from normal individuals activated for 4 days with PHA or PMA + ionophore was not influenced by the presence of anti-Fas antibody. When the same cells were activated with soluble factors produced by previously activated T-cells (lymphostimulatory activity), anti-Fas antibodies inhibited thymidine incorporation by 74+/-4%. The presence of typical morphological changes and oligonucleosomal fragmentation of DNA indicated that the reduced proliferation resulted from apoptotic death of the lymphoblasts. Fas-sensitivity of T-cells activated by lymphostimulatory activity was first detectable 4 days after activation, and at 5 days the majority of lymphoblasts had become sensitive to Fas, whereas no evidence of sensitivity to Fas was observed for lymphoblasts generated by PHA or PMA + ionophore during the first 5 days of culture. Incubation of cells activated with PHA or PMA+ ionophore in the presence of IL-2 at concentrations 10-fold higher than that present in lymphostimulatory activity did not induce early sensitivity to Fas, indicating that exposure to IL-2 could not explain the precocious development of sensitivity to Fas seen following activation by lymphostimulatory activity. These studies demonstrate that T-cells activated through an antigen-independent 'alternative' pathway develop precocious sensitivity to Fas-induced apoptosis, which may be important in permitting the elimination of autoreactive bystander cells activated in the course of immune responses.

Extensive apoptosis of lung T-lymphocytes maintained in vitro.

The phenotypic and functional properties of T cells recovered from the lung indicate that many of these cells have been recently activated. Because such recently activated cells are often more susceptible to death through apoptotic mechanisms, the viability of lung T cells recovered from bronchoalveolar lavage and those isolated from peripheral blood was compared. The progressive loss of viable cells following in vitro culture was considerably greater for lavage T cells than blood T cells, and was observed for cells from both patients with sarcoidosis and control subjects. Following 4 days of culture, 76 +/- 14% of blood cells, but only 31 +/- 13% of lavage cells from sarcoid patients were viable. The evaluation of morphologic features and flow cytometric profiles, as well as the demonstration of typical oligonucleosomal fragmentation of DNA extracted from these cells indicated that lavage T cells were dying by apoptotic mechanisms. CD4+ T cells appeared to be particularly sensitive to apoptosis. Most lavage T cells from controls and sarcoid patients expressed Fas (CD95) antigen. Although some lavage T Cells were sensitive to Fas-induced apoptosis, the viability of lavage T cells was not improved by incubation in the presence of a monoclonal antibody that inhibits Fas-induced apoptosis. Culture in the presence of interleukin 2 did prevent, at least in part, the progressive death of lavage T cells, suggesting that the viability of T cells in the lung may depend on the presence of locally delivered trophic signals. These studies emphasize that T cells on the alveolar surface are in a different state of activation and differentiation compared with that of circulating T cells, and offer a possible explanation for the impaired functional capacities observed for lavage T cells in some in vitro studies.

Role of granulocyte-macrophage colony stimulating factor (GM-CSF) in the pathogenesis of adult pulmonary histiocytosis X.

BACKGROUND: Pulmonary histiocytosis X is a disorder characterised by the presence of destructive granulomas preferentially involving distal bronchioles, that contain numerous activated Langerhans' cells. Recent studies have shown that granulocyte-macrophage colony stimulating factor (GM-CSF), which is produced by normal bronchiolar epithelium, may play an important part in the distribution and differentiation of Langerhans' cells. The aim of this study was to evaluate the role of this factor in the pathogenesis of pulmonary histiocytosis X. METHODS: Four patients with pulmonary histiocytosis X were examined by immunohistochemical techniques for GM-CSF and CD1a surface molecules. RESULTS: In early lesions the epithelium of bronchioles affected by the disease was strongly positive for GM-CSF and infiltrated by numerous CD1a+ Langerhans' cells organised into granulomas. In contrast, the expression of GM-CSF was substantially lower in bronchioles not affected by the disease, and these bronchioles contained few Langerhans' cells. When destruction by histiocytosis X lesions was more advanced, only remnants of bronchiolar epithelium could occasionally be identified; these remained strongly reactive for GM-CSF. Langerhans' cells within granulomas also moderately expressed this cytokine. CONCLUSIONS: These results support the hypothesis that GM-CSF could be one of the factors responsible for the local accumulation of lymphostimulatory Langerhans' cells in early lesions of pulmonary histiocytosis X.

Expression of heat shock proteins in human lung and lung cancers.

Heat shock proteins (HSP) are highly conserved molecules whose expression is induced in eukaryotic cells following a broad spectrum of environmental stresses. These proteins can also be expressed by virally transformed cells and cancer cells and are important targets for T lymphocytes. Little is known about the abundance and distribution of HSP in the normal lung, the effect of cigarette smoking on their expression, or their expression in human lung carcinomas. We have used monoclonal antibodies coupled with immunohistochemical and immunoelectrophoretic techniques to evaluate the distribution of four different HSP (HSP 90 kD, HSP 73 kD/constitutive, HSP 72 kD/inducible, and HSP 63 kD) in normal lung (n = 14) and lung cancers (n = 15). In lung tissue from nonsmokers (n = 7), bronchiolar epithelial cells were intensely positive for HSP 90 kD and HSP 72 kD/inducible and weakly reactive for HSP 63 kD. Most macrophages also expressed these HSP at low levels, but no other parenchymal or immune/inflammatory cells were positive. Cigarette smoking did not modify the distribution or the intensity of HSP in bronchiolar epithelial cells, and macrophages from smokers expressed similar or lower levels of these HSP. Tumor cells from 14 of 15 lung carcinomas expressed one or more of the HSP. Considerable heterogeneity in the expression of HSP by cells in a given tumor was observed, explained in part by differences in the differentiation of the cells. Detection of HSP by immunohistochemical and immunoelectrophoretic techniques gave similar results for HSP 72 kD/inducible and HSP 90 kD.(ABSTRACT TRUNCATED AT 250 WORDS)

Surface phenotype of Langerhans cells and lymphocytes in granulomatous lesions from patients with pulmonary histiocytosis X.

Pulmonary histiocytosis X (HX) is a disorder characterized by the presence of granulomas in which Langerhans cells (LC) and lymphocytes are abundant. Although the pathogenesis of pulmonary HX remains unknown, an uncontrolled immune response initiated by LC, which are potent antigen-presenting cells in vitro, may play an important role. To further characterize LC and lymphocytes present in granulomas from these patients, we used immunohistochemical techniques and monoclonal antibodies to evaluate the surface phenotype and electron microscopy (EM) to seek evidence for close interactions between both cell types in these lesions. In all samples, HX granulomas contained large numbers of strongly positive CD1a cells in which typical Birbeck granules were identified by EM. The number of Birbeck granules in LC from HX granulomas was strikingly increased compared with that in LC in the bronchioles of normal subjects. Furthermore, unlike normal LC, essentially all LC in HX granulomas expressed CD4 antigens and were strongly positive for CD1c. Lymphocytes infiltrating HX granulomas were almost entirely CD3+ T cells and were mainly CD4 positive (CD4/CD8 ratio 3.7 +/- 1.3). These T lymphocytes expressed almost exclusively alpha/beta T cell receptors, and gamma/delta T cells were rarely observed (< 5% of CD3+ cells). In areas of lymphocytic infiltration, close differentiated contacts between LC and lymphocytes were observed by EM in all samples. These results demonstrate that interactions between activated LC and CD4+ T lymphocytes are prominent in early HX granulomas and support the idea that an immune response in which LC serve as accessory cells is involved in the pathogenesis of this disorder.