Acute stress induces rapid and significant changes in WBC, monocyte, neutrophil, lymphocyte, and Th, CTL, B, and NK cell numbers in the blood. Leukocyte numbers (1000 /μl blood) were quantified at 0 (baseline) and 6, 15, 30, 60, and 120 minutes during restraint stress. An increase in immune cell numbers relative to baseline represents mobilization of leukocytes into the blood. A decrease from peak numbers or relative to baseline represents trafficking of cells out of the blood and into tissues. Percent change relative to baseline at peak and trough is indicated. Data are expressed as means ± SEM (n=3). Statistically significant differences are indicated: * p < 0.05, and ** p < 0.01: relative to baseline (Fisher's LSD); † p < 0.05, and †† p < 0.01: relative to peak (Fisher's LSD).