F8 levels in transgenic and post-BMT mice. (A-D) Antigenic levels in platelet lysates (open bars), and releasates (gray bars), and plasma (black bars) were measured. Panels A and B were transgenic mice expressing pF8 studies and panels C and D were BMT/lentiviral pF8 studies. All mice were FVIII^null. Background measurements in FVIII^null mice were subtracted from expressed F8 levels. Mean ± 1 SD are shown. The numbers of animals studied in each arm are shown above each bar. Panel A shows the transgenic IR8 studies and panel B the pcBF8. The highest expressing phBF8 line previously studied phF8.3817 is included as positive control. Panels C and D show similar data for BMT/lentiviral pF8 studies. U indicates studies with the lentivirus driven by the ubiquitin promoter and P indicates studies with the PF4 promoter. BMT38 were FVIII^null mice reconstituted with marrow from the phF8.38 transgenic line as positive control. (E) Activity level of F8 from platelet releasate (open bars) and plasma (gray bars).