INCREASED NUMBERS OF HYPODENSE EOSINOPHILS IN THE BLOOD OF PATIENTS WITH BRONCHIAL-ASTHMA

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Abstract
We investigated the density of blood eosinophils from patients with asthma using polyvinylpyrrolidone-coated silica gel (Percoll) discontinuous density gradient centrifugation of peripheral blood leukocytes. Ten patients with allergic asthma, 10 normal subjects, and 2 patients with the hypereosinophilic syndrome (HES) were studied. The density distribution profiles of eosinophils from normal subjects showed: (1) peaks at densities of 1.085 to 1.090 g/ml and (2) inflection points or nadirs near 1.082 g/ml, below which only 10% of eosinophils were found. On the basis of these results, we divided eosinophils into 2 subpopulations: normodense (> 1.082 g/ml) and hypodense (< 1.082 g/ml). Densities of eosinophils from patients with asthma and HES peaked at 1.083 and 1.076 g/ml (mean values), respectively, significantly lighter than eosinophils from normal donors (p < 0.005 and p < 0.001, respectively). The proportions of hypodense eosinophils in patients with asthma and HES were 35 and 95%, respectively, and were significantly greater than that in normal donors (p < 0.002 and p < 0.001, respectively). The density distribution profiles of a normal subject were stable over time, but those of asthmatic patients varied with time. For the 22 participants, there was a positive correlation between log-transformed blood eosinophil counts and the percentage of hypodense eosinophils (r = +0.86, p < 0.001). Similarly, for 15 of them, plasma eosinophil granule major basic protein correlated with the numbers of peripheral blood eosinophils (r = +0.92, p < 0.0005) and hypodense eosinophils (r = +0.92, p < 0.0005). Thus, a portion of the eosinophils in asthmatic patients and most of the eosinophils in patients with HES are hypodense. Although the reason for this hypodensity of eosinophils is unknown, it may reflect the release of immature eosinophils from bone marrow, and/or the activation of eosinophils in the peripheral circulation.