Immunohistochemical characterization of hepatic lesions associated with Elaeophora elaphi parasitism in red deer (Cervus elaphus).

This study was based on the immunohistochemical characterization of hepatic lesions caused by Elaeophora elaphi in 15 red deer. In eight animals filariae were found in branches of the portal vein. "Web-like" endophlebitis (15 cases), lymph nodule-like thrombi associated with filarial debris (12 cases) and fibrinous thrombi (three cases) were also observed in the portal vein. Multifocal granulomatous hepatitis (six cases) and lymph nodule-like tissue (three cases) were found in the liver parenchyma. The distribution of CD3 antigen, IgG-lambda light chains, and S-100 protein in lymphoid tissue in the portal vein thrombi and hepatic parenchyma was similar to that found in the cortex of the lymph nodes. In these lesions, lymphoid follicles with large germinal centres (mainly composed of IgG+ B lymphocytes, with occasional S-100+ follicular dendritic cells) predominated over interfollicular lymphoid tissue (mainly composed of CD3+ T lymphocytes and S-100+ interdigitating cells). This suggested that the local humoral immune response was more important than the cellular response in this parasitic disease. The presence of interdigitating and follicular dendritic cells confirmed the high degree of organization of the abnormal lymphoid tissue and suggested that antigen presentation to T and B lymphocytes and the subsequent proliferation of the latter was particularly efficient in such tissue. The latter may therefore be superior to diffuse granulomatous infiltrate in terms of the production of a local immune response.