Subset-selective up-regulation of CXCR1 by CD8⁺ T cells stimulated with PHA. CD8⁺ T cells were stimulated with PHA (10 μg/mL for 15 minutes) and expression of CXCR1 assessed on maturation subsets as defined by expression of CCR7 and CD45RA. Up-regulation was most prominent on CD8⁺ T cells with a central memory phenotype (ie, CCR7⁺ CD45RA^–). Each symbol indicates an individual experiment and donor.