Immunohistochemical characterization of hepatic lesions associated with migrating larvae of Ascaris suum in pigs

This paper describes the histopathological features and the cellular distri bution of T lymphocytes (CD3), B cells (CD79a), immunoglobulin (IgG, IgA, I gM)-bearing plasma cells, macrophages (Mac387 and alpha-1-antitrypsin), MHC class II antigen and S-100 protein in hepatic white spots associated with naturally occurring Ascaris suum parasitism in 35 pigs. Hepatic granulomas were observed in 10 pigs, whereas lymphoid proliferation with a diffuse or lymphonodular pattern was the main histopathological lesion in immunoreacti ve cells with all antibodies tested was closely similar to that found in th e cortex of lymph nodes. Thus, lymphoid follicles were composed mainly of C D79a(+) B cells and interfollicular tissue was composed mainly of CD3(+) T lymphocytes. The presence of follicular dendritic and interdigitating cells expressing S-100 protein and MHC class II antigen in lymphonodular lesions suggested that these are highly organized structures developed to enhance antigen presentation to B and T cells, and consequently the local immune re sponse against the parasite. The humoral local response was represented mai nly by IgG-secreting plasma cells. (C) 2001 Harcourt Publishers Ltd.