Morphogenesis and pathogenesis of chronic lung diseases. XVII. Ultrastructure of the experimentally induced granulomas of the rabbit lung.

Experimentally induced lung granulomas of rabbits challenged by complete Freund's adjuvant with human gammaglobulins were ultrastructurally studied at two moments of their evolution: 10 and 20 days. Granulomas were formed even in the first stage, being composed of histiocytic accumulations around capillaries, sometimes dilated, in which the adjuvant lipidic compounds were embolized: hypertrophy of endothelial cytoplasms, lymphocytic insertions with membrane contacts with the histiocytes, an epithelial covering completed this picture. The 20-day granulomas presented intragranulomatous capillaries with hypertrophied endothelia, macrophages and lymphocytes; the pericapillary granulomatous tissue showed many epithelioid cells with mitochondria and numerous cytoplasmic vesicles of different densities (among them "grey vesicles"), and long cytoplasmic digitations; some histiocytes had an epithelioid aspect. A large granulous alveolocyte was sometimes present at the granuloma periphery. The perinodular veins evinced hypertrophied endothelia with many pinocytotic vesicles and coated caveolae expressing the processing of engulfed transported particles; fibroblasts were active near veins.