Confocal laser-scanning immunofluorescence microscopy using frozen sections of a liver specimen from a patient with hepatitis C–related chronic hepatitis. Immunofluorescence labeling with anti-ADAMTS13 antibodies showed intense green fluorescence in the perisinusoidal cells, which were irregular in shape with spotty, oval, unipolar, and bipolar cytoplasmic processes extending between the hepatocytes (A). Red fluorescence indicated α-SMA immunoreactivity, reflecting the fact that these cells were activated HSCs (B). Colocalization of ADAMTS13 (A) and α-SMA (B) in single cells yielded yellow color in the merged figure (C). (Original magnification, × 400; bar = 30 μM in A-C.)