Fig. 4.

Kinetics of infection of IL-2- independent cell lines by wild type and adapted FIV-PPR. Infections were performed and monitored for the presence of reverse transcriptase activity as detailed in Section 2. (A) Both 3201 cells and 104-C1DL cells are resistant to productive infection with FIV-PPR. However, FIV-PPRglial, which arose from long-term culture of FIV-PPR on 104-C1DL cells, will productively infect both 3201 cells and IL-2 independent 104-C1DL cells. (B) Addition of exogenous IL-2 to the IL-2 independent cells does not render them susceptible to productive infection by FIV-PPR and adaptation occurs at equivalent rates with and without IL-2.