HIV-1_BaL infection of in vitro-differentiated, monocyte-derived, human DCs. Flow cytometry was used to phenotypically characterize immature DCs generated from plastic adherent monocytes (A) or control DCs generated from monocytes isolated from PBMCs by negative selection (B) obtained after 6 days of culture in the presence of IL-4 and GM-CSF by determining the frequencies of CD1a⁺, CD3⁺, and CD14⁺ cells. Immature DCs were exposed to 2 different doses (1 × or 10 ×) of the CCR5-using isolate HIV-1_BaL. The frequency of HIV-1_BaL-infected DCs was determined by intracellular p24 staining after 4, 24, 48, 52, and 72 hours of virus exposure (C). The figure shows median values of 5 individual donors. Immature DCs (D, top row) or control DCs (D, bottom row) were exposed to 10 × HIV-1_BaL for 72 hours or the virus was washed off after overnight incubation and cultured for 72 hours in the absence or presence of 10 μM AZT. Gates were set on large CD1a⁺ CD3^- cells. The frequency of HIV-1_BaL-infected DCs was determined by intracellular p24 staining after 72 hours.