IMMUNOHISTOCHEMICAL IDENTIFICATION OF ITO CELLS AND THEIR MYOFIBROBLASTIC TRANSFORMATION IN ADULT HUMAN LIVER

To identify Ito cells in normal and pathological adult human livers, i mmunohistochemical studies were performed by the avidin-biotin-peroxid ase complex method using monoclonal antibodies for a-smooth muscle act in (ASMA), desmin, and vimentin. Fifty one needle biopsies, 7 surgical ly resected specimens, and 5 autopsy specimens were studied. In the no rmal adult liver vascular smooth muscle cells and pericytes, together with perisinusoidal cells with thin cytoplasmic processes were positiv e for ASMA. These latter cells formed a loose and discontinuous layer along the sinusoidal walls. Immunoelectron microscopy showed that the ASMA-positive perisinusoidal cells were Ito cells containing fat dropl ets. The other sinusoidal lining cells were negative for ASMA. In chro nic liver disease, ASMA-positive Ito cells showed an increase in numbe r, size, and the intensity of immunostaining in areas of piecemeal nec rosis), and formed a continuous cellular network. These cells were den dritic in shape with irregularly elongated cytoplasmic processes and c ontained an increased amount of microfilaments, in association with lo ss of the characteristic fat droplets. Thus, their ultrastructural fea tures corresponded to those of myofibroblastic cells. Ito cells showed no staining for desmin in both normal and pathological livers. These results indicate that immunohistochemistry using an anti-ASMA antibody is a sensitive and reliable method for the identification of both nor mal and transformed Ito cells in adult human livers.