FIG. 1.

HYB PRO BMDCs shed virus and transmit infection to other cell types. (A) Viral RNAs isolated from the supernatants (SUP) of HYB PRO (HP) BMDC cultures were analyzed by RT-PCR for MMTV sequences. The supernatants of C3H/HeN BMDCs and HYB PRO genomic DNA were used as negative and positive controls, respectively. (B) HYB PRO BMDCs were cocultured for 3 days with uninfected C3H/HeN BMDCs, C3H/HeN primary B cells, and NMuMG mammary gland cells in the presence of a 0.4-μm barrier filter. +, coculture with HYB PRO BMDCs; −, coculture with C3H/HeN BMDCs. DNAs from the recipient cells were prepared, and viral DNA was detected by PCR with MMTV-specific primers. TRH3 and 293T cells were used as positive and negative controls for infection, respectively. The data are representative of three experiments with similar results.