CXCR4 and infection: Regarding CXCR4 expression levels in different subsets, the frequencies of CD34+CD7+CXCR4+ cells in HIV+ samples (mean 2.08 ± 2.56%) were significantly reduced compared to those in HIV− samples (mean 2.49 ± 2.42%) (Figure 6B right), regardless of the degree of infection (data not shown).