Effect of β chemokines on the replication of the M-tropic HIV-1 strain Yu-2 in the DC-T cell coculture model. DC were pretreated with the respective chemokine (500 ng/mL) for 60 minutes, followed by exposure to Yu-2 (3 ng of p24) for 2 hours in the continued presence of chemokines. The cells were then washed five times to remove virus and cocultured with PHA-induced, uninfected syngeneic T cells in medium containing IL-2. No further chemokine treatment was performed during this phase II. The medium was changed every 2 days.