Density profile of bronchoalveolar lavage eosinophils in the guinea pig model of allergen-induced late-phase allergic responses.

Inhalation of aerosolized ovalbumin by guinea pigs both during sensitization and upon challenge induces a pulmonary eosinophilia as assessed by cells recovered in bronchoalveolar lavage fluid (BALF). In comparison with BALF eosinophil numbers in naive animals of 0.82 +/- 0.2 x 10(6) cells, those in sensitized animals before challenge and 17 and 72 h after challenge were 1.48 +/- 0.2 x 10(6), 2.60 +/- 0.6 x 10(6), and 4.2 +/- 0.7 x 10(6) cells, respectively. BALF eosinophils from all these groups were notable for their heterogeneity with respect to density, size, and appearance under the electron microscope. In comparison with peritoneal eosinophils, which had a single mean density peak of 1.088 +/- 0.001 g/ml, BALF cells comprised hypodense (less than 1.080 g/ml), normodense (1.080 to 1.096 g/ml), and hyperdense (greater than 1.096 g/ml) eosinophils. The percentage of hypodense eosinophils rose from 25% in naive animals to 63% in sensitized animals (P less than 0.001) and fell after challenge. In contrast, challenge induced the appearance of hyperdense eosinophils, which rose from 6% in sensitized animals to 42% 72 h after challenge (P less than 0.001). Blood eosinophils in naive animals showed a similar profile to those in the lung, but after sensitization and challenge no gross changes in the proportion of either hypodense or hyperdense eosinophils were observed. Flow cytometric analysis of BALF eosinophils indicated that hypodense eosinophils, with a mean diameter of 15.8 microns, were larger than both normodense and hyperdense eosinophils, which had mean diameters of 14.3 and 11.6 microns, respectively. Although the numbers and size of granules were not reduced in hypodense BAL eosinophils, electron microscopy morphology indicated a reduced granular content.(ABSTRACT TRUNCATED AT 250 WORDS)