Phenotypic analysis of infiltrating cells in human myocarditis. An immunohistochemical study in paraffin-embedded tissue

To define the cellular subpopulations that infiltrate the heart in human myocarditis, formaldehyde-fixed, paraffin-embedded sections from 18 hearts with histologically proved myocarditis were examined immunohistochemically. Disease was classified on routine stains as follows: mixed mononuclear cell (7 cases), granulomatous (3), giant cell (1), rheumatic (2), and fungal (5) myocarditis, respectively. On immunohistochemical examination, T-lymphocyte and macrophage predominance was found in nearly every case, except in fungal myocarditis, in which polymorphonuclear leukocyte and macrophages prevailed. In contrast, B lymphocytes and natural killer cells were conspicuously absent, regardless of histologica classification. Giant cells in giant cell myocarditis and in the Aschoff lesions of rheumatic carditis expressed macrophage, but not myocyte, antigens, suggesting derivation along macrophage lineage. Immunohistochemical data obtainable in paraffin-embedded tissues supplement the study of myocarditis, providing information potentially relevant to immunopathogenesis, natuarl history, and therapy.