Morphologic and Histochemical Evaluation of Alveolar Macrophages
The AM from liquid paraffin pneumonitis demonstrated morphologic abnormalities. Nearly all the AM had a foamy appearance because the cytoplasm was full of numerous, large, rounded vacuoles (Fig 2). These optically empty vacuoles were not stained with the May-Grunwald-Giemsa, Papanicolaou or PAS. Vacuoles were weakly stained in black with Sudan B and in orange with Sudan III. Oil Red O intensively stained in red nearly all the AM, supporting the presence of neutral lipids as the main constituent of the vacuoles.
The cytoplasm of AM from normal subjects was basophil, microvacuolated in relation to the lysosomes and phagosomes, but never displayed large empty vacuoles such as those found in liquid paraffin pneumonitis. The AM of patients with PAP displayed a foamy cytoplasm but the vacuoles were smaller and contained amorphous material which was strongly PAS-positive and dark stained with Oil red O. Their nuclei often were pyknotic, and they were surrounded by an abundant extracellular proteinaceous material, also PAS-positive. ventolin inhaler
Electron microscopic evaluation of the AM from liquid paraffin pneumonitis confirmed the existence of large, numerous, empty vacuoles throughout all the cytoplasm and surrounded by a thin osmiophil line (Fig 3). Few areas of normal cytoplasm were present between these large vacuoles and the number of intracellular organelles was reduced. The size of the AM appeared to be in the normal range. Their plasma membranes were very irregular with many pseudo-podes. Some AM exhibited smaller vacuoles containing slightly osmiophil and partially retracted material.
Figure 2. Optic micrograph of alveolar macrophages recovered bylavage from a patient with liquid paraffin pneumonitis and stained with oil Red O. The cytoplasm is full of large and small rounded vacuoles that push back the nucleus (oil red O, original magnification X 1000).
Figure 3. Electron micrograph of an alveolar macrophage recovered by lavage from a patient with liquid paraffin pneumonitis. The cytoplasm contains large, empty vacuoles, some of which are surrounded by an osmiophilic line (arrow) (original magnification x 4700).