Cellular immune response in popliteal lymph nodes and liver of dogs with visceral leishmaniasis

Resumo

Canine visceral leishmaniasis (CVL) is a zoonosis caused by Leishmania (Leishmania) infantum chagasi in the American continent. There are few studies detailing the immunopathological characteristics in lymph nodes and liver in infected dogs in endemic area from Teresina city, Piauí State, Brazil. Thus, we have evaluated histopathological changes and the presence of CD4⁺ and CD8⁺ T cells in popliteal lymph nodes and liver of nine dogs with clinical manifestation (G1) and seven dogs without clinical manifestation (G2) naturally infected with L. (L.) infantum chagasi. Histopathological and immunohistochemical analysis were performed on samples liver and lymph nodes tissues. The important clinical changes were lymphadenopathy (80%) and skin lesions (70%). Histopathological analysis of the popliteal lymph node revealed higher depletion cell of the paracortical region. The number of CD4⁺ and CD8⁺ T cells was no significant between the groups but there was positive correlation between CD4⁺ and CD8⁺ T cells in G1 and G2. In the liver, the inflammatory infiltrate was focal consisting of mononuclear cell in the periportal and intralobular regions, in both groups. Inflammatory infiltrate of mononuclear cells showed positive staining for CD4 and CD8 T cells but there was no significant difference between groups. However, there was a positive correlation between CD4⁺ and CD8⁺ T cells in the G1. Immunoperoxidase analysis also revealed more amastigotes and antigen of Leishmania in G1 in liver and lymph nodes than in G2. The role of CD4⁺ and CD8⁺ T cells seems is not related to the clinical status of dogs with CVL.