In vivo studies on hemopoietic stem cells and target cells for Friend virus infection in vitro.

Friend virus replicating target cells have been characterized by in vitro infection of bone marrow cells from DBA/2 mice after multiple injections of hydroxyurea (HU), after bleeding and/or hypertransfusion and after busulfan treatment. The concentration of CFUS, BFUE and CFUE in the cell suspension was correlated with the number of infectious centers (IC) induced after infection. HU treated mice were also infected in vivo. The results demonstrate that there is almost no target cell 4 h after the last of 4 HU injections. The number of IC induced could correlate with the numbers of CFUS in the HU experiment, but this possibility can be rejected based on the busulfan experiments. All results, including those after bleeding and/or hypertransfusion are compatible with a target cell between BFUE and CFUE, as suggested by other in vitro infection methods and also in vivo experiments.