Giant cell reaction against the laminated membrane of echinococcus cysts in reindeer lungs.

In 23 pairs of lungs from reindeer two to five years of age, two types of hydatid cysts of Echinococcus granulosus were found: typical well-developed cysts and collapsed degenerated cysts. Collapsed cysts were found in 13 pairs of lungs, well-developed in nine pairs, while both types of cysts were found in one pair of lungs. A giant cell formation was present in the innermost zone of the surrounding adventitial membrane of both collapsed cysts and well-developed cysts. The giant cell reaction seemed to be induced by and directed against the laminated membrane. In the areas of the cysts where the laminated membrane showed a close contact with the adventitial membrane, the giant cells seemed to be actively engaged in the inflammatory process. On the contrary, in the areas of the cysts where the laminated membrane had lost contact with the adventitial membrane, the giant cells were degenerated or necrotic, and the space between the membranes was filled with necrotic cells. In cases where the laminated membrane had been pronouncedly disintegrated, the giant cells were also necrotic or nonexistent. The giant cell reaction which was found even in comparatively young fertile cysts suggests that the reindeer variant of E. granulosus, if such exists, is not especially well-adapted to the reindeer as its intermediate host.