Inflammatory Cell Distribution within and along Asthmatic Airways

Pulmonary and Critical Care Division, Departments of Medicine and Departments of Surgery and Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
American Journal of Respiratory and Critical Care Medicine (Impact Factor: 13). 08/1998; 158(2):565-72. DOI: 10.1164/ajrccm.158.2.9705036
Source: PubMed


Asthmatic airways are infiltrated with inflammatory cells that release mediators and cytokines into the microenvironment. In this study, we evaluated the distribution of CD45-positive leukocytes and eosinophils in lung tissue from five patients who died with severe asthma compared with five patients with cystic fibrosis. For morphometric analysis, the airway wall was partitioned into an "inner" area (between basement membrane and smooth muscle) and an "outer" area (between smooth muscle and alveolar attachments). Large airways (with a perimeter greater than 3.0 mm) from patients with asthma or cystic fibrosis had a greater density of CD45-positive cells (p < 0.05) and eosinophils (p < 0.001) in the inner airway region compared with the same airway region in small airways. Furthermore, in small airways, asthmatic lungs showed a greater density of CD45-positive cells (p < 0.01) and eosinophils (p < 0.01) in the outer compared with the inner airway wall region. These observations indicate that there are regional variations in inflammatory cell distribution within the airway wall in patients with asthma that are not observed in airways from patients with cystic fibrosis. We speculate that this inflammatory cell density in peripheral airways in severe asthma may relate to the peripheral airway obstruction characteristic of this condition.

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    • "The mucosal epithelial layer of the airways plays a pivotal role in the non-specific host defense of the respiratory tract and in shaping both innate and adaptive immune responses of the respiratory system [1,2]. In asthma, the hypertrophy of submucosal glands and hyperplasia of goblet cells in the airways [3] form the basis of excessive mucus production, leading to sometimes fatal bronchial plugging. Furthermore, many of the pathological features of asthmatic tissues such as tissue injury and inflammation are triggered in part by mediators derived from the airway epithelium [1,4]. "
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    ABSTRACT: The airway epithelium is thought to play an important role in the pathogenesis of asthmatic disease. However, much of our understanding of airway epithelial cell function in asthma has been derived from in vitro studies that may not accurately reflect the interactive cellular and molecular pathways active between different tissue constituents in vivo. Using a sheep model of allergic asthma, tracheal explants from normal sheep and allergic sheep exposed to house dust mite (HDM) allergen were established to investigate airway mucosal responses ex vivo. Explants were cultured for up to 48 h and tissues were stained to identify apoptotic cells, goblet cells, mast cells and eosinophils. The release of cytokines (IL-1α, IL-6 and TNF-α) by cultured tracheal explants, was assessed by ELISA. The general morphology and epithelial structure of the tracheal explants was well maintained in culture although evidence of advanced apoptosis within the mucosal layer was noted after culture for 48 h. The number of alcian blue/PAS positive mucus-secreting cells within the epithelial layer was reduced in all cultured explants compared with pre-cultured (0 h) explants, but the loss of staining was most evident in allergic tissues. Mast cell and eosinophil numbers were elevated in the allergic tracheal tissues compared to naïve controls, and in the allergic tissues there was a significant decline in mast cells after 24 h culture in the presence or absence of HDM allergen. IL-6 was released by allergic tracheal explants in culture but was undetected in cultured control explants. Sheep tracheal explants maintain characteristics of the airway mucosa that may not be replicated when studying isolated cell populations in vitro. There were key differences identified in explants from allergic compared to control airways and in their responses in culture for 24 h. Importantly, this study establishes the potential for the application of tracheal explant cultures in relevant ex vivo investigations on the therapeutic and mechanistic modalities of asthmatic disease.
    Journal of Inflammation 08/2010; 7(1):46. DOI:10.1186/1476-9255-7-46 · 2.02 Impact Factor
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    • "It is possible that airway preparations are relatively impermanent to the direct application of MBP. Several investigators have qualitatively noted MBP within the airway wall of patients with asthma [4, 5, 19, 20]. But, in none of these studies was an analysis of the MBP performed such that the granule protein localization could be differentiated between intracellular and extracellular deposition, nor was a precise localization of the eosinophils in relative distance and distribution to myocytes and airway neurons established. "
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    ABSTRACT: Major basic protein (MBP) released from activated eosinophils may influence airway hyperresponsiveness (AHR) by either direct effects on airway myocytes or by an indirect effect. In this study, human bronchi, freshly isolated human eosinophils, or MBP purified from human eosinophil granules were incubated for studying eosinophil infiltration and MBP localization. Eosinophils immediately adhered to intact human airway as well as to cultured human airway myocytes and epithelium. Following incubation 18-24 h, eosinophils migrated into the airway media, including the smooth muscle layer, but had no specific recruitment to airway neurons. Eosinophils released significant amounts of MBP within the airway media, including areas comprising the smooth muscle layer. Most deposits of MBP were focally discrete and restricted by immunologic detection to a maximum volume of approximately 300 microm(3) about the eosinophil. Native MBP applied exogenously was immediately deposited on the surface of the airway, but required at least 1 h to become detected within the media of the airway wall. Tissue MBP infiltration and deposition increased in a time- and concentration-dependent manner. Taken together, these findings suggest that eosinophil-derived cationic proteins may alter airway hyperresponsiveness (AHR) in vivo by an effect that is not limited to the bronchial epithelium.
    Mediators of Inflammation 03/2010; 2010(0962-9351):824362. DOI:10.1155/2010/824362 · 3.24 Impact Factor
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    • "Alternatively, it can be questioned whether the bronchial epithelial tissues obtained were representative for the study. As shown in earlier studies in human COPD and asthma patients, there is variability of distribution of inflammatory cells in bronchial tissue which can require examination of biopsies from more than one airway generation to increase the statistical power to detect differences between individuals [25,26]. Of the six biopsies we obtained from each horse, the first two were from the first generation bronchus and examined by PCR. "
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    ABSTRACT: The aim of this study was to evaluate the contribution of bronchial epithelium to airway inflammation, with focus on mRNA and protein expression of cytokines of innate immunity IL-6, IL-10 and TNF-alpha, in horses with Recurrent Airway Obstruction (RAO) during exacerbation and in remission. Despite marked clinical and physiologic alterations between exacerbation and after remission in the RAO horses no differences were detected in either cytokine mRNA or protein levels. Moreover, the expression of investigated cytokines in RAO horses on pasture did not differ from controls. In comparing real-time PCR analysis to results of immunohistochemistry only IL-10 mRNA and protein levels in RAO horses on pasture were significantly correlated (rs = 0.893, p = 0.007). Curiously, in controls examined on pasture the TNF-alpha protein level was positively correlated to IL-10 mRNA expression (rs = 0.967, p = 0.007) and negatively correlated to IL-6 mRNA expression (rs = -0.971, p = 0.001). Given the complementary relationship of assessing cytokines directly by immunohistochemistry, or indirectly by PCR to mRNA, the lack of significant changes in either mRNA or protein levels of IL-6, IL-10 or TNF-alpha mRNA in RAO horses in exacerbation suggests that these particular cytokines in bronchial tissue may not play a substantive role in the active inflammation of this disease. To support this contention further studies examining time dependency of expression of IL-6, IL-10 or TNF-alpha are needed, as is expansion of the range of cytokines to include other key regulators of airway inflammation.
    BMC Veterinary Research 02/2008; 4(1):8. DOI:10.1186/1746-6148-4-8 · 1.78 Impact Factor
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