Immunohistochemical characterization of Kisselev nodules in wild boars (Sus Scrofa L.).

Kisselev nodules have been described in several parasitic infestations, even if their functional role and mechanisms of formation are not completely understood. The aim of the study was to investigate, for the first time, the T (CD3) and B lymphocytes (CD79acy), macrophages (lysozime, alpha1antitrypsin) and follicular dendritic cells (CNA.42) distribution and vascular organization (vWF) of Kisselev nodules observed in wild boars. Tissue samples (lungs, kidneys, livers, tracheo-bronchial lymph nodes, spleens) were collected by 47 hunted wild boar, fixed in 10% buffered formalin, embedded in paraffin and stained with haematoxylin-eosin. Kisselev nodules were observed in lung (n=9), liver (n=1) and kidney (n=1), composed of lymphoid follicle-like structures with small amounts of interfollicular diffuse lymphoid tissue. The distribution of immunoreactive cells was similar to the cortex of lymph nodes: lymphoid follicles with germinal centers (composed mainly of CD79+ B cells, especially in the outer corona) predominate over interfollicular tissue (composed mainly of CD3+ T lymphocytes). These findings, in the cases associated with worms infections, suggest that the local humoral immune response is more important than the cellular response in parasitic diseases. The presence of follicular dendritic cells, involved in the antigen presentation and clonal expansion of B and T cells, confirms the high degree of organization of these lymphoid-like structures. Basing on the findings of similar structures in human chronic diseases (ectopic follicle, lymphoid neogenesis, tertiary lymphoid tissue), we can suggest, in the different cases, the following hypothesis about their genesis: (1) a direct derivation from BALT; (2) a primary involvement of monocytes/macrophages or follicular dendritic cells (major source of specific chemotactic factors for lymphoid cells, such as BCA-1); (3) the role played by the vascular system and the adhesion molecules expressed on the endothelial cells in the migration and recruitment of specific cells and the development of chronic inflammation.[...]