Immunoreactivity patterns of CLL mAbs with intracellular structures of live human cells. Healthy HEp-2 cells were fixed, permeabilized, and exposed to 50 µg/mL of mAbs 114 (A,B), 657 (C), 845 (D), 366 (E), and 255 (F). Binding was detected with FITC-labeled goat anti-human IgG. Standard immunofluorescence microscopy images (A,C–F). Confocal microscopy showing mAb 114 binding to fiberlike structures suggestive of cytoskeletal components (B). Studies by Chu et al. indicate that vimentin is the target of this mAb (49).