MYOCARDIAL INFLAMMATORY INFILTRATE IN HUMAN CHRONIC CHAGASIC CARDIOMYOPATHY - IMMUNOHISTOCHEMICAL FINDINGS

Chagas' disease is the most common form of chronic myocarditis in the world. It is characterized by a progressive chronic myocarditis that l eads to cardiomegaly, arrhythmias, cardiac failure, and thromboembolic phenomena. This communication reports studies on the immunohistochemi stry of chronic infiltrates in 30 endomyocardial biopsies and in contr acting and specialized myocardium of autopsies of four patients suffer ing from Chagas' cardiomyopathy. Expression of the following antigens was studied: common leucocyte antigen (CLA-CD45R), L-26(CD20), CD68, k appa and lambda light chains and T-UCLH-1 (CD45RO), and MB-1. Streptav idin-peroxidase and streptavidin-alkaline phosphatase with biotinylate d anti-mouse IgG were used as detection systems. Double immunostaining for the simultaneous demonstration of T lymphocytes (CD45RO) and macr ophages was performed using both immunoenzymatic techniques consecutiv ely. Expression of CD31 was detected for the demonstration of endothel ial cells. In endomyocardial biopsies, tissue forms of trypanosomes we re not found. The percentage of fibrous tissue was 24.1% +/- 12.8% (ra nge 8.2%-49%). Eosinophils were scarce (1/high-power field), but assoc iated with necrotic areas of the myocardium. Mast cells were scarce or absent. They were always situated in fibrotic areas. The most remarka ble finding was the presence of infiltrates consisting of macrophages and CLA-positive mononuclear cells. Twenty-six and one-half percent of them were T lymphocytes, and 10.5% were B lymphocytes. Lymphocytic in filtration was particularly associated with necrotic and degenerative myocardial lesions. Thirty percent of the infiltrate was composed of m acrophages (positive CD68 cells). The remaining infiltrate was compose d of mononuclear cells resembling macrophages and CLA-negative mononuc lear cells. Contacts between CD68-positive cells and T lymphocytes wer e frequently found. CD31 antibodies clearly pointed out normal endothe lial cells, in either normal or damaged vessels. No isolated cells pos itive for these antibodies were found within the mononuclear infiltrat e. In autopsied hearts, myocardial lesions consisted of a chronic infl ammatory process with fibrotic scars and extensive mononuclear infiltr ates. No amastigote nests were found. A statistically significant diff erence (p < 0.05) was obtained when the percentage of fibrosis was com pared in the specialized and contracting myocardiums (51.6% +/- 18% vs . 43.4% +/- 8%). Eosinophils were scarce in infiltrates, reaching 5%, and they were associated with necrotic myocardium. Mast cells also wer e scarce or absent in specialized and in contracting myocardium. Almos t all the lymphocytic population was T lymphocytes. Such infiltrates w ere more prominent in the working myocardium (39%) and in the speciali zed cells of the left branch of the His bundle than in the atrioventri cular node and in the right Hisian branch (34.4%). The 31% of mononucl ear cells were CD68 positive, thus corresponding to macrophages. Conta cts among T lymphocytes and macrophages were frequently observed. Alth ough much that is concerned with Chagas' cardiomyopathy is controversi al, these may be the major ingredients for its pathogenesis: the paras ite or a part of it, lymphocytes and macrophages, and fibrosis. Then a multifactorial or ''combined theory'' may be suggested to explain the sequence of events that lead to the chronic stage of the disease.