Immunohistochemical detection of TGF-b in paratuberculosis granulomatous lesions

VERNA A, GARCÍA-PARIENTE C, MORENO O, REYES LE, BENAVIDES J, PAOLICCHI F1, ROMANO MI2, GARCÍA MARÍN JF, PÉREZ V

Copenhaguen. Denmark

Congreso; 8th International Colloquium on Paratuberculosis; 2005

“In situ” detection of TGF-b in different types of lesion associated with MAP infection was completed using histochemical methods. Samples of intestine (ileocaecal valve, ileum and jejunum) with and without lymphoid tissue and mesenteric lymph nodes were obtained from lambs and calves experimentally infected with MAP. The Avidin-Biotin Peroxidase technique was employed using a polyclonal antibody against human TGF-b. Lesions present in the samples were classified as: focal (formed by small granulomas, with no or very low number of mycobacteria located in the lymphoid tissue and seen in the initial or latent stages of the infection); and diffuse forms (composed of an extensive granulomatous infiltrate located in the lymph nodes and intestinal lamina propria, showing moderate to large amounts of bacilli and seen in the advanced stages of MAP infection). In all the cases, positive immunolabelling was absent or seen sporadically in macrophages forming focal granulomas, both located in the lymph node or intestinal lymphoid tissue. However, in diffuse granulomatous lesions present in the intestinal mucosa, the majorities of macrophages were TGF-b positive and showed a high intensity of staining. A clear relationship was seen between the presence of high numbers of bacteria in the cytoplasm and the intensity of the staining. These results suggest that high levels of TGF-b could be related to the inability of macrophages to kill MAP and thus the progression of the infection. Low levels of TGF-b, seen in focal lesions, could be related to the initial phases or forms of resistance of the infection. Key words: Pathology, granulomas. immunohistochemistry. TGF-b.