T lymphocytes and macrophages in the intestinal tissues of dogs infected with Leishmania infantum

Linfócitos T e macrófagos nos tecidos intestinais de cães infectados com Leishmania infantum

Abstract

This study was about a semi-quantitative analysis of T lymphocytes (CD4⁺ and CD8⁺, FoxP3⁺ regulatory T cells), and macrophages in the gut wall of dogs naturally infected with Leishmania infantum. Thirteen dogs were divided into three groups: group 1 (G1, n=5), dogs with canine visceral leishmaniasis (CVL) and infected with L. infantum amastigotes in the intestine; group 2 (G2, n=5), dogs with CVL but without intestinal amastigotes; and group 3 (G3, n=3), uninfected dogs (control group). There was no significant difference (p ≥ 0.05) on CD4⁺ and Treg cell numbers among the groups, whereas the levels of CD8⁺ T cells and macrophages were significantly higher in dogs from G1 group than in G2 and G3 (p ≤ 0.05), especially in intestinal segments with high parasite burden. Parasite burden correlated positively with levels of CD8⁺ T cells and macrophages (p ≤ 0.05), but was inversely correlated to levels of CD4⁺ T lymphocytes and FoxP3⁺ Treg cells. In conclusion, in the intestine of dogs with CVL, the increase of CD8⁺ T cells and macrophages population associated with high parasite burdens, but no changes of CD4⁺ T cells and FoxP3⁺ Treg cells suggest a possible immunoregulation by the parasite not dependent on Treg cells.

Keywords:
T lymphocytes; macrophages; canine visceral leishmaniasis; intestinal tract