Immunohistochemical observations on cellular response in unilocular hydatid lesions and lymph nodes of cattle
Introduction
In hydatidosis in animals and humans, an immune granulomatous reaction that includes mononuclear cell infiltration and intensive pericystic fibrosis is a histopathological feature of hydatid lesions. From murine experiments, Ali-Khan (1978) suggested cellular immunity influences the development of the pericystic granulomatous reaction in hydatid lesions. Draining lymph nodes increase in weight and lymphocyte blast transformation increases in the early stages of the infection in mice inoculated with protoscoleces of Echinococcus granulosus (Riley et al., 1984). However, lymphocyte responses revert to pre-infection responses during 3–8 weeks post infection (p.i.) (Riley et al., 1986). However, regressive or progressive alveolar hydatid lesions appear to be correlated with granulomatous cell composition and the proportion of T-cell subpopulations in lesions in experimentally infected mice (Bresson-Hadin et al., 1990). In our previous survey on hydatidosis in cattle (Sakamoto et al., 1987), the bovine hydatid cysts were classified into four types: unilocular, polymorphic, multicystic and involutional. Regressive changes at varying degrees were observed in the majority of the hydatid cysts of each of the four types, especially in involutional cysts. Severe infiltration and accumulation of numerous eosinophils and infiltration of lymphocytes and macrophages were seen in the adventitial tissue surrounding hydatid cysts. We believe an immunohistochemical study of the lymphocyte subpopulations in the pericystic adventitia of bovine hydatid lesions and in the local lymph nodes has not been done. This study investigated the relationship between such cells as lymphocyte subpopulations, macrophages and eosinophils infiltrating the adventitial tissue of hydatid lesions, and draining lymph nodes and the progressive or regressive change in hydatid cysts.
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Materials and methods
Hydatid lesions and draining lymph nodes were collected from 65 cattle having infected liver and from 87 cattle having infected lungs in abattoirs in Uruguay. Some of the collected material was fixed in 10% neutral formalin and the rest of the material was fixed in other fixatives. Paraffin sections were prepared. The sections were stained by various methods such as hematoxylin-eosin, pyronin-methyl green, Bieblich scaret-hematoxylin, periodic acid-Schiff, Azan and others for histological
Histopathology of hydatid lesions in the liver and lungs
The hydatid lesions from all cattle having the infected liver and lungs were histologically examined. All hydatid cysts were sterile, and were classified into 58% unilocular, 22% polymorphic, 0.5% multicystic and 1.5% involutional cysts. Regressive changes at varying degrees were at a high level in each of the four types, especially in most of the involutional cysts. In initial hydatid lesions, unilocular cysts were surrounded with an epithelioid cell layer and an adventitial layer (Fig. 1). A
Discussion
In our study, the smallest unilocular hydatid cysts were surrounded by an epithelioid cell layer composed of mononuclear cells bound to a laminated layer. The cells were a kind of histiocyte from GM/M MoAb positive reaction and morphological features. These cells have usually been considered to be derived from macrophages, and our study has confirmed this view.
In most cattle having larger mature hydatid cysts, CD8+ cells were predominant in the pericystic adventitial layer, which also had fewer
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