An investigation into the nature of giant cells in cardiac and skeletal muscle.

In an immunohistochemical study of six cases of giant cell myocarditis, the typical giant cells have been shown to express up to four different macrophage-associated antigens, but not desmin, the intermediate filament protein characteristic of muscle cells. These results support the view that the giant cells have a macrophage rather than a myogenic origin. In contrast, the giant cells found in regenerating skeletal muscle have the immunophenotype of muscle cells and not of macrophages supporting their muscle origin.