Collagen immunotyping of the hepatic fibrosis in human alveolar echinococcosis.

An extremely dense fibrosis is responsible for the main complications of alveolar echinococcosis (AE), a severe parasitic disease due to the development in the liver of a larval form of the cestode Echinococcus multilocularis. Immunotyping of collagens present in fibrous, granulomatous, and normal areas of the liver was performed in nine patients with AE. Immunofluorescent labelling of collagen types showed that dense fibrosis was entirely composed of thick bundles of type I and type III collagens, surrounding old parasitic vesicles with an autofluorescent laminated layer. In granulomatous areas, collagens were labelled as clusters consisting mainly of type III procollagen and collagen. Concentric bundles of type III collagen surrounded active parasitic vesicles. An enhancement of the normal labelling in portal spaces of the intact liver was present in all the patients. These results suggest that irreversible acellular keloid scar-like fibrosis observed in AE is the ultimate result of cytotoxic and fibrogenetic events related to the immune response of the host which are taking place initially in the granulomatous area surrounding the young parasite larvae.