Mast cells in the human alveolar wall: an electronmicroscopic study.

Abstract

SUMMARY Mast cells were identified by electronmicroscopy in the alveolar wall of the lung in 20 subjects (10 normal, 10 abnormal). A quantitative and qualitative study was made of the mast cells. In the normal lung there was an average concentration of 350 mast cells/mm2 of alveolar wall and in the abnormal 523/mm2. Mast cells occupied approximately 1-6-2-1 % of the area of the alveolar wall. There was marked variation in the structure of the mast cell granules but no differences between those in the normal and abnormal lungs. There was evidence that constant degranulation of mast cells may be occurring in the lung. The role that alveolar mast cells may play in the vasoconstrictor response to alveolar hypoxia is discussed. It is suggested that the tachypnoea present in asthma may partly be due to release of mediators from sensitised mast cells within the alveolar wall.It has been generally thought that mast cells in the human lung are found deep to the bronchial mucous membranel 2and also around blood vessels particularly venules deep in connective tissue. 3 During the course of routine electronmicroscopic study of human lungs we were suprised to see mast cells within the alveolar wall. We therefore studied systematically by electronmicroscopy both qualitatively and quantitatively the distribution of mast cells within alveoli in normal and abnormal human lung tissue. Material and methodsLung tissue was obtained by thoracotomy from 20 patients of which lung disease was present in 10 ( Table 1). The assessment of disease in the lung was made by examining paraffin sections of lung tissue adjacent to the areas from which the sections for electronmicroscopy were taken. A piece of lung tissue (about 1 cm x 1 cm x 0-5 cm) was taken immediately after the specimen was removed, and placed in Karnovsky fixative at 4°C: after one hour the tissue was cut into pieces approximately 2 mm x 2 mm x 1 mm and allowed to fix for a further three hours. The specimens were washed overnight in cacodylate-sucrose buffer at 4°C, then postfixed in 1 % osmium tetroxide for one hour at 4°C. This was Accepted for publication 6 May 1981 followed by washing in distilled water for five minutes and block staining in 2 % aqueous uranyl acetate for one hour. The tissue was dehydrated to absolute alcohol and placed in two changes of epoxypropane for 15 min each, and then in warmed (60°C) Araldite for one hour. The tissue was then embedded in fresh Araldite at 600Cfor at least 48 h. Sections were cut at 2 ,urm, stained with toluidine blue, and areas showing alveolar walls were selected for ultrathin sections. These were then cut with gold interferencecolourmounted on G200 HT copper grids and contrasted with 2 % uranyl acetate and lead citrate and examined in a Philips EM 201.

Pseudomonas aeruginosa Exotoxin A Induces Human Mast Cell Apoptosis by a Caspase-8 and -3-dependent Mechanism

“…Mast cells are abundant in the lung, occupying ϳ1.6 -2.1% of the area of the alveolar wall (36). Importantly, many human lung mast cells directly protrude through the alveolar wall into air space (36), which allows direct interaction between mast cells and pathogens.…”

“…Mast cells are abundant in the lung, occupying ϳ1.6 -2.1% of the area of the alveolar wall (36). Importantly, many human lung mast cells directly protrude through the alveolar wall into air space (36), which allows direct interaction between mast cells and pathogens. Recently, we demonstrated active interactions between human mast cells and P. aeruginosa, resulting in the secretion of mast cell-derived cytokines and chemokines that are important in innate immunity (37 -FIG.…”

Histopathological and ultrastructural aspects of mice lungs experimentally infected with dengue virus serotype 2

“…Increase of mast cells in the peribronchiolar space and adjacent to the interalveolar septa in lung of mice in our experiments, probably contributes to the permeability changes seen in this organ. Tissue mast cells probably are activated and also involved in DEN injury, since they are usually found in normal and abnormal alveolar wall (Fox et al 1981). They produce a series of vasoactive mediators, including histamine and histamine-like products.…”

An Ultrastructural Study of Mast Cells in the Alveolar Wall of Normal and Asthmatic Lung

“…However, in normal lung we observed more (64-2%) granules of 'scroll'and 'combined'type, while in asthmatic lung the majority (59-7%) of granules were 'particulate' or 'empty'. If we accept the hypothesis that during the mediators release the structure of mast cell granules changes from 'scroll' and 'combined' to 'particulate' and 'empty' (Trotter and Orr, 1973;Kawanami et aL, 1979;Fox et al, 1981), then our data suggest that the degranulation process is more marked in asthmatic tissue than in normal. This contradicts the data obtained by Fox and associates (1981), who found that the scale of degranulation was the same in normal and pathological lung tissue, but supports the findings of Connell (1971) and Kawanami and co-workers (1979) that degranulation is more common in pathological than in normal lung.…”

“…While most studies of pulmonary mast cells have concentrated on their presence in the bronchial tree (Connell, 1971;Patterson and Suszko, 1971;Austen and Orange, 1975;Jeffery and Corrin, 1984), recent studies have shown that mast cells are also present in alveolar structures (Kawanami et al, 1979;Fox, Bull and Guz, 1981;Agius et ai, 1984;Tomioka et al, 1984). However, very little data on mast cell content and structure within the alveolar wall in normal and diseased lung are available.…”