Immunohistochemical observations on cellular response in unilocular hydatid lesions and lymph nodes of cattle

Abstract

As we believe the immunohistochemistry of the hydatid lesions and draining lymph nodes has never been studied, we collected them from the liver and lungs of cattle in Uruguay for such a study. Frozen sections of the tissues were immunohistochemically stained using monoclonal antibodies against surface markers CD2, CD4, CD5, CD8, B cell and granulocyte-monocyte/macrophage and antiserum against specific granules of bovine eosinophils. The adventitial layer of the cyst wall consists of a layer of epithelioid cells and connective tissue. The cells from the epithelioid cell layer were a kind of macrophage. In most cases having progressive hydatid cysts, CD8+ cells were predominant in the pericystic adventitia, and a relatively small number of CD4+ cells were in the same area. In the adventitial layer surrounding the regressive and involutional hydatid cysts, infiltrating lymphocytes were composed mostly of CD4+ cells. An eosinophil-mediated destruction of the laminated layer was recognized in the regressive and involuted hydatid cysts. The subpopulations of T cells in the local lymph nodes tended to be similar to T cells in the adventitial layer of hydatid lesions. From our findings, we consider that infiltration of eosinophils and the subpopulations of lymphocytes infiltrating the hydatid lesions in the liver and lungs are derived from cells in the draining lymph nodes of both organs.

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.