CXCR4 and CCR5 expression on uninfected, bystander, and productively infected cells. CD4⁺ T cells were isolated and infected as indicated earlier. The cells were then stained for p24 and CXCR4 or CCR5. (A,D) Mock-infected cells. (B,E) Bystander cells. (C,F) HIV productively infected cells. Histograms shown are representative of 3 donors.