Some electron microscopy characteristics of lung immune response in the rats stimulated by respiratory and parenteral ways with pneumococcal suspensions.

Conventional albino rats of either sexes, weighing about 100 grams, were stimulated, one group by inhalation of pulverized suspensions of living type III pneumococci, in 6 exposures, and the second group, by 5 intramusculary injections, one a week, of 0,1 ml, emulision of killed germs, in complete Freund's adjuvant submitted after a week free interval to the inhalation of aerosolized living pneumococci. The tissue fragments sampled at two and respective five weeks after the beginning of the experiment, from central and peripherical sites of lungs, inclusively from a control group, were fixed in glutaraldehide-osmic acid and prepared for electron-microscopical examination. In the thickened, densely cellular alveolar walls there are numerous mature plasma cells, intermediate elements between reticular septal cells and plasmablast and also histiocytic cells which phagocytic inclusions and shape suggests their movement in the interalveolar septa. The swollen free alveolar macrophages contain an increased number of lysosomes and ribosomes. The hyperplastic granular pneumocytes possess enlarged cytosomes excreting osmiophilic material in the air spaces. There are discussed the problems of local plasma cell differentiation, alveolar macrophage physiology and transparietal migration of histiocytes.