Leishmaniose visceral canina: estudo quantitativo e comparativo da expressão do receptor do complemento do tipo 3 (CR3 CD11b/CD18) com alguns aspectos histológicos e parasitológicos do baço, fígado e linfonodos de cães naturalmente infectados com Leishmania (Leishmania) chagasi

Abstract

The aim of this work was to evaluate some clinical, histopathological, parasitological and immunological aspects of dogs naturally infected with Leishmania chagasi. The principal aim was to compare the third receptor of complement CR3 (CD11b/CD18) in spleen, liver, lymph nodes (axilar, cervical and polpliteal) with clinical, histological and parasitological findings. This study was carried out with ten control dogs (uninfectedanimals) and thirty infected dogs. All them was mongrel dogs with undefined age and was obtained from the municipality of Belo Horizonte, metropolitan area. The infected animals were divided in two groups: (1) group denominated asymptomatic composed by ten animals without clinical signs of the disease; (2) group denominated symptomatic composed by twenty animals with classical clinical signs of the disease as skin lesions (alopecia, eczema and ulcers), loss weight and lymphopathy. During necropsy, fragments of spleen, liver, lymph nodes (axillary, cervical, and popliteal) and skin (ears, nose and abdomen) were collected and fixed with formaldehyde solution 10% for histological analysis. Paraffined sections of all tissues were mounted on histological slides and stained by Hematoxylin-Eosin (H&E) and the strepto-avidinperoxidase immunohistochemical method for microscopical and parasitological analysis, respectively. Frozen tissue sections of all organs, except skin samples, were stained by the strepto-avidin peroxidase immunohistochemical method for CR3 (CD11b/Cd18) tissue characterization. The tissue and cellular CR3 expression was evaluated by morphometrical digital analysis. Densitometrical CR3 expression washigher in infected animals than controls, but it was not different when compared between animals with different defined clinical status. CR3 cell expression in spleens was higher in symptomatic animals than in asymptomatic ones where the parasite load was higher. In another side, CR3 cell expression in livers was higher in asymptomatic animals than in symptomatic ones, where the tissue parasite load was lower. However,there was a positive correlation between the parasite load and cellular CR3 expression in the spleens and cervical lymph nodes of infected dogs and there is a negative correlation in liver. We can say, that the immune response appears to be organ specific (immune response compartmentalization) whereas inflammatory cells play a distinctrole. Sometimes, they could act to perpetuate the infection or they could act as effector cells in order to control the infection. Following our results where the symptomatic animals showed higher parasite loads and higher CD11b/CD18 expression in their lymphoid organs as spleen and lymph nodes, we can conclude that these cells (monocyte-macrophages) might serve to perpetuate intracellular infection.