In vivo kinetics of circulating eosinophils and other blood cells after glucocorticoid administration in 3 species. Twenty healthy human volunteers received a single IV dose of glucocorticoid (methylprednisolone, 250 mg). Four adult rhesus macaques received a single IV dose of glucocorticoid (methylprednisolone, 4 mg/kg). Ten adult B6.SJL mice were randomly divided into 2 groups. One group (n = 5) received a single IV dose of glucocorticoid (methylprednisolone, 5 µg/g). Another group (n = 5) received vehicle (normal saline) at the same volume as the glucocorticoid-treated animals. The cell composition of peripheral blood was assayed by automated CBCs in a clinical laboratory. (A) Blood composition among the 3 species, at BL and in response to glucocorticoid (GC). The relative proportion of each color corresponds to the mean percentage of the respective cell type in the species displayed. WBC, white blood cell. (B) Top: relative abundance (expressed as a percentage of total WBCs) of eosinophils in peripheral blood, before and after glucocorticoid administration, in each of the 3 species. Bottom: AEC in peripheral blood, before and after glucocorticoid administration, in each of the species. In human and rhesus macaque cells, values at BL and in response to glucocorticoid (4 hours) are shown. In mice, values in vehicle- or glucocorticoid-treated animals are shown. Error bars represent the mean ± SD. Statistical analyses of the human and rhesus data were performed with a paired Student t test. Statistical analysis of the mouse data was performed with a Student t test for independent samples.