FIG. 2.

Expression levels of CCR5, CXCR4, and Ki67 in memory and naïve resting CD4⁺ T cells. The level of expression of the HIV coreceptors CCR5 and CXCR4 and the level of expression of the cellular activation markers Ki67 were assessed by flow cytometry. A subset of memory cells (dashed oval) expressed higher levels of CCR5 than did most memory cells. Minimal expression of the cell cycle marker Ki67 was detected in the memory subset, and no expression was detected in the naïve cells. Unstained cells were used to show the background level for CXCR4 and CCR5 staining. An isotype control was used to determine the background level for the Ki67 intracellular staining.