Restriction of N-MLV. A, MDTF or D17 cells expressing TRIM5αhu, TRIM5αAGM, or control cells were infected with multiple dilutions of N-MLV and B-MLV vectors expressing GFP. The percentage of infected cells was determined by flow cytometry. B, MDTF or D17 cells expressing various orthologues of TRIM5α, or expressing TRIMCyp, were infected with GFP-expressing N-MLV or B-MLV vectors. The virus dose used in each cell type was first adjusted so that 5–10% of control cells would be infected and the same volume of virus preparation was then used to infect the various TRIM5-expressing cell lines from that cell type. The percentage of infected cells was determined 2 days later by flow cytometry, and results are shown as % of the values obtained for the control cells. The experiment was carried out in triplicates, and standard deviations are shown.