Immunohistochemical localization of laminin in the hearts of patients with chronic chagasic cardiomyopathy: relationship to thickening of basement membranes

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 leads to cardiomegaly, arrhythmias, cardiac failure, and thromboembolic phenomena. This communication reports studies on the immunohistochemistry of chronic infiltrates in 30 endomyocardial biopsies and in contracting and specialized myocardium of autopsies of four patients suffering from Chagas' cardiomyopathy. Expression of the following antigens was studied: common leucocyte antigen (CLA-CD45R), L-26(CD20), CD68, kappa and lambda light chains and T-UCLH-1 (CD45RO), and MB-1. Streptavidin-peroxidase and streptavidin-alkaline phosphatase with biotinylated anti-mouse IgG were used as detection systems. Double immunostaining for the simultaneous demonstration of T lymphocytes (CD45R0) and macrophages was performed using both immunoenzymatic techniques consecutively. Expression of CD31 was detected for the demonstration of endothelial cells. In endomyocardial biopsies, tissue forms of trypanosomes were not found. The percentage of fibrous tissue was 24.1% ± 12.8% (range 8.2%-49%). Eosinophils were scarce (1/high-power field), but associated with necrotic areas of the myocardium. Mast cells were scarce or absent. They were always situated in fibrotic areas. The most remarkable 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 infiltration was particularly associated with necrotic and degenerative myocardial lesions. Thirty percent of the infiltrate was composed of macrophages (positive CD68 cells). The remaining infiltrate was composed of mononuclear cells resembling macrophages and CLA-negative mononuclear cells. Contacts between CD68-positive cells and T lymphocytes were frequently found. CD31 antibodies clearly pointed out normal endothelial cells, in either normal or damaged vessels. No isolated cells positive for these antibodies were found within the mononuclear infiltrate. In autopsied hearts, myocardial lesions consisted of a chronic inflammatory process with fibrotic scars and extensive mononuclear infiltrates. No amastigote nests were found. A statistically significant difference (p < 0.05) was obtained when the percentage of fibrosis was compared 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 were scarce or absent in specialized and in contracting myocardium. Almost all the lymphocytic population was T lymphocytes. Such infiltrates were more prominent in the working myocardium (39%) and in the specialized cells of the left branch of the His bundle than in the atrioventricular node and in the right Hisian branch (34.4%). The 31% of mononuclear cells were CD68 positive, thus corresponding to macrophages. Contacts among T lymphocytes and macrophages were frequently observed. Although much that is concerned with Chagas' cardiomyopathy is controversial, these may be the major ingredients for its pathogenesis: the parasite 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.

Pathogenesis of chronic Chagas' myocarditis: An overview

The evidence provided by both human and animal studies on chronic Chagas' heart disease suggests that the development of the chronic fibrosing myocarditis is related to progressive and additive focal cellular necrosis with associated inflammatory lymphomononuclear infiltrate, reactive and reparative myocardial fibrosis, surrounding myocyte hypertrophy. These processes may be initiated and perpetuated by alterations in the myocardial microcirculation and by autoimmune factors. These findings could foster future therapeutic strategies in the management of chronic chagasic patients to optimize the medical treatment and hopefully to improve prognosis.

Chagas' disease and the autoimmunity hypothesis

The notion that the pathology of Chagas' disease has an autoimmune component was initially based on the finding of circulating antibodies binding heart tissue antigens in patients and mice chronically infected with Trypanosoma cruzi. Later, T lymphocytes reactive with heart or nerve tissue antigens were found in chagasic mice and patients, extending the concept to include cell-mediated immunity. However, there is disagreement about whether the observed immunologic autoreactivities are triggered by T. cruzi epitopes and then affect host tissue antigens by virtue of molecular mimicry or are elicited by host antigens exposed to lymphocytes after tissue damage caused by the parasite. There is also disagreement about the relevance of immunologic autoreactivities to the pathogenesis of Chagas' disease because of the lack of reproducibility of some key reports supporting the autoimmunity hypothesis, conflicting data from independent laboratories, conclusions invalidated by advances in our understanding of the immunologic mechanisms underlying cell lysis, and, last but not least, a lack of direct, incontrovertible evidence that cross-reacting antibodies or autoreactive cells mediate the typical pathologic changes associated with human Chagas' disease. The data and views backing and questioning the autoimmunity hypothesis for Chagas' disease are summarized in this review.

Human chagasic disease is not associated with an antiheart humoral response

An inflammatory cardiomyopathy occurs in humans with chronic Trypanosoma cruzi infection (Chagas' disease). This study finds that T. cruzi infection is not associated with the production of cardiac-specific autoantibodies in humans with cardiac manifestations.

Antibodies to laminin and immunohistochemical localization of laminin in chronic chagasic cardiomyopathy: a review

Antibodies against laminin were determined by ELISA in forty six patients suffering from Chagas' disease and twenty healthy persons (control group). The patients were divided into three groups according to the severity of clinical, electrocardiographic and echocardiographic studies. Histologic, ultrastructural and immunohistochemical studies were made of endomyocardial biopsy specimens from 10 of these patients with chronic Chagasic cardiomyopathy. Antibodies to laminin were detected in 50% of the patients in each of the three groups. However analysis of the data did not allow us to determine any significant correlation among the severity of the different clinical and non-invasive studies and the level of circulating antibodies to laminin. The highest titers of antilaminin antibodies were detected in the group with severe cardiological alterations (37% of the patients). Histological and electron microscopic observation of myocardial biopsies disclosed marked thickening of the basement membranes of the myocytes, endothelial cells and vascular smooth muscle cells. Light (peroxidase-labeled antibodies) and electron (gold-conjugated antibody) microscopic immunohistochemical methods revealed a positive reaction for laminin in these thickened basement membranes. This thickening may develop as a consequence of: a) an immunologic reaction which is triggered by the presence of a laminin-like molecule on the surfaces of T. cruzi amastigotes and trypomastigotes; b) an immunologic response to direct injury of basement membranes causing some of their components to become antigenic; c) myocardial fibrosis, with synthesis of new connective tissue components, and d) a combination of the preceding factors. The relationship of these changes to antilaminin antibodies remains unclear.(ABSTRACT TRUNCATED AT 250 WORDS)