HEp-2 immunofluorescent staining of control antibodies. Anti-FVIII monoclonal mAb, isotype controls or human recombinant FVIII alone do not bind to HEp-2 cells, whereas immune complexes of anti-FVIII mAb plus FVIII produce a cytoplasmic reticular staining pattern like that observed in 6 patients with AHA (bottom row, compare Figure 1D).