HIV infection of immature DC. (A) Kinetics of p24 production: Culture day 8 sorted CD1a⁺ DC were exposed 1 day later to 500 TCID₅₀ of HIV-1_LAI (□) or HIV-1_Ba-L (○), and further cultured with GM-CSF/TNF-/IL-4; virus production in supernatants is expressed as ng of p24/10⁵ viable cells; p24 levels in heat-inactivated virus–exposed DC were always <0.1 ng/10⁵ viable cells. (B) Morphologic examination of cells on day 8 PI with HIV-1_Ba-L, showing that DC are involved in typical syncitia. Results of one of three experiments.