Figure 2.

Bronchiolar epithelium in chronic allergy: semithin sections of lung embedded in araldite resin and stained with toluidine blue (a and c); paraffin sections stained with AB/PAS (b and d). In control lung, the epithelium was thin and the secretory Clara cells stained strongly with toluidine blue (arrows), which delineates in dark blue the secretory granules under the plasma membrane (a). Control lungs were negative after AB/PAS stain (b). After chronic exposure to OVA, the epithelium was tall, with non-ciliated cells appearing as a wide apical cytoplasm that stained pale with toluidine blue. Ciliated cells (arrowheads) appeared in a basal position in relation to non-ciliated cells. A thick stromal layer, composed of collagen, fibroblasts and smooth cells, underlay the epithelium (c). An intense AB/PAS stain was observed in bronchioles exposed to chronic inflammation (d). Bars represent 20 μm in (a) and (c), and 200 μm in (b) and (d).