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

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.