Chemotactic activity of SDF-1 and CKβ-11/MIP-3β/ELC on thymocytes is sensitive to pertussis toxin. Low-density total thymocytes were preincubated with pertussis toxin at indicated concentrations for 1 hour and used for chemotaxis to SDF-1 (300 ng/mL) and CKβ-11/MIP-3β/ELC (500 ng/mL). Data are expressed as the mean percentage of inhibition (±differences of duplicated experiments). Complete inhibition (100%) means that chemotaxis to chemokines is inhibited to background or lower than background levels, and no inhibition (0%) represents maximum chemotaxis to chemokines observed without pertussis toxin treatments. Partial inhibition is between 0% and 100%. *Significant inhibition (P < .05) from controls (no pertussis toxin treatment).