Bovine apoB-100 is present on the cell surface and is found intracellularly. (A) Trypsin-treated BW and (B) BL6.9 ES cells were stained by 3E8.1-FITC with or without saponin permeabilization. The staining medium contained PBS only. (C) Permeabilized BW cells were stained with 3E8.1-FITC or isotype-matched control antibodies and then stained with Alexa Fluor 488 conjugated goat antimouse IgG.