Ultrastructural observations on sinusoidal endothelial cells in chronic active hepatitis.

Ultrastructural features of 12 liver biopsies from patients with chronic active hepatitis were studied, particular attention being paid to endothelial cells. In areas of piecemeal necrosis and parenchymal inflammation sinusoidal endothelial cells show swelling of the cytoplasm, protrusion of the cell body into the sinusoidal lumen, increase in micropinocytotic vesicles and appearance of numerous dense bodies. This cell type is termed 'active endothelial cell'. Subsequent changes include enlargement of the Golgi complex, increase of rough endoplasmic reticulum in cytoplasmic processes with concomitant decrease of dense bodies, appearance of a fuzzy coat and formation of hemidesmosomes in close relationship to basement membrane-like material and reticulin fibres in the space of Disse. The latter ultrastructural characteristics correspond to those of 'fibroblastic reticulum cells' described in lymph nodes. Active endothelial cells and fibroblastic reticulum cells may play a protective role in liver parenchymal inflammation by reducing the accessibility of noxious agents from the blood stream to liver parenchymal cells, and be crucial in the initiation of perisinusoidal fibrosis.