Expression of inflammatory chemokine receptors on activated versus nonactivated CD8⁺ T cells. (A) Expression of CXCR1, CX3CR1, CXCR3, and CCR5 was assessed on CD8⁺ T cells ± PHA (15 minutes, 20 μg/mL). Gray shaded histograms represent baseline expression, open closed-line histograms represent expression after activation. The vertical line indicates the cut-off for positivity as determined by isotype-control antibodies (not shown). No PHA-induced up-regulation was observed for CXCR3, CCR5, and CX3CR1 (representative of n = 3). By contrast, substantial PHA-induced up-regulation was observed for CXCR1 (representative of n = 6). (B) Time-course (n = 6; PHA at 10 μg/mL), (C) dose response (n = 6; activation for 15 minutes). *P < .01 as compared with baseline; **P < .001 as compared with baseline. (D) Impact of inhibition of protein synthesis (CHX) and inhibition of actin polymerization (CytD) (n = 3; PHA stimulation at 10 μg/mL for 15 minutes). Up-regulation of CXCR1 after nonspecific CD8⁺ T-cell stimulation occurred within seconds/minutes, in a dose-dependent manner and independently from protein synthesis, but was largely abolished by inhibiting actin polymerization. Error bars indicate mean ± SD.