Infiltration of DP macrophages at the site of myocarditis. Myocarditis was induced in FW-wt rats by immunization with porcine myosin and the adjuvant containing killed tuberculosis germs at 3 weeks of age. Three weeks later, the heart was extirpated and used for histologic and immunocytochemical examinations. Experiments were repeated twice. Representative results are shown. (A) Hematoxylin and eosin staining. (B-C) Immunohistochemical staining for CD68 (ED-1) and CD3 (IF4), respectively. The cardiac tissues were cut into small pieces and digested with 0.16% collagenase type II. After removal of tissue fragments, cell suspension was incubated in a plastic dish at 37°C. One hour later, adherent cells were harvested and immunofluorescent triple staining was done for CD68 (ED-1, green; D), CD4 (OX-35, red; E), and CD8 (OX-8, blue; F). (G) The merged image. Arrowheads indicate DP macrophages also stained for CD68. Total magnification: × 40 (A-C), × 80 (D-F), and × 200 (G).