Estudo da heterogeneidade de monócitos de cães infectados ou não por Leishmania infantum

Abstract

Peripheral blood monocytes are the largest group of circulating progenitor cells. Its functions have been revealed through the study of their subpopulations, especially in humans and mice in pathological processes from infectious or noninfectious chronic diseases. Among the studied infectious diseases there is the leishmaniasis, which the most severe is the visceral leishmaniasis. Protozoa of the genus Leishmania are obligate intracellular parasites in cells of the mononuclear phagocyte system of the mammalian host, as monocytes, macrophages and dendritic cells. The dog (Canis familiar) is the main reservoir of this parasite, having a central role in the transmission to humans. In Brazil, the parasite Leishmania (Leishmania) chagasi (syn. L. infantum) is the main cause of the canine visceral leishmaniasis. This study aimed to characterize subpopulations of peripheral blood monocytes from uninfected or L. infantum naturally infected dogs and compare their phonotypical and functional aspects. Blood samples were collected from dogs from different groups: uninfected (n=5) and infected (asymptomatic (n=5) and symptomatic (n=5) with L. infantum. Cells were labeled by antibodies against the molecules: CCR2, CD11a, CD11b, CD11c, CD14, CD16, CD44, CD45RO, CD56, CD62L, CD80, CX3CR1 e MHC-II and the samples were obtained by flow cytometry. CD14+ cells represented about 4% of the total leucocytes and when analyzing those cells, it was observed two distinct populations according to CD14 expression: a population with high expression of CD14 (CD14hi), constituting about 90% of the monocytes showing basophilic and horseshoe-shaped nucleus with greater phagocytic capacity, and another with low expression of CD14 (CD14lo), constituting about 10% of monocytes, showing less basophilic and kidney-shaped nucleus. The analysis of the other molecules showed different levels of expression between the two populations. In dogs with visceral leishmaniasis no difference in frequency was observed between populations, however there is an increase of CD14+ cells in infected dogs. We also noticed marked reduction of the expression of molecules related to the activation of monocytes (CCR2, CD11c, CD45RO, CD62L and MHC-II), especially in the group of symptomatic dogs, indicating a possible inhibition on the capacity of these cells to control the disease.