Intracellular expression of wt-fVIII and N1922S-fVIII in BHK-M cells. Confluent monolayers of BHK-M cells expressing wt-fVIII or N1922S-fVIII were permeabilized with Triton X-100 and incubated with the anti-A2 MAb 4A4. After washing, the cells were incubated with goat anti–mouse IRDye 800CW secondary antibody. Infrared fluorescence emission of the secondary antibody was detected at 800 nm and quantitated densitometrically as described in “Immunocytochemical assay of fVIII.” Results are reported as mean and sample standard deviation (n = 4 per construct).