Immunodetection of MIF in Lymph Nodes of Dogs with Visceral Leishmaniasis - Abstract
In canine Visceral Leishmaniasis (VL), the presence of generalized lymphadenopathy is commonly observed in animals with chronic disease. It is known that parasite Leishmania (Leishmania) infantum modulates host immune system, thereby favoring its multiplication. The aim of this study was to evaluate the immunodetection of macrophage migration inhibition factor (MIF) in lymph nodes (popliteal, subscapular, iliac and mesenteric) of naturally infected dogs (asymptomatic and symptomatic) by this protozoan. A set of 33 naturally infected dogs from an endemic area for VL were sampled and another set of five dogs negative for VL and from a non-endemic area were analyzed as the control group. Detection of MIF and parasite load of internal and peripheral lymph nodes of dogs with VL and controls was made by immunohistochemistry. Parasite load was observed only in lymph nodes of infected dogs and differed
significantly (P<0.05) from control group. MIF cytokine was detected predominantly on macrophages and lymphocytes in all lymph nodes of all groups. Popliteal lymph node of symptomatic dogs had the highest number of immunomarked cells for MIF, especially in granulomas. Significant differences (P<0.05)
among infected and control groups occurred only in popliteal and mesenteric lymph nodes. Additionally, amastigotes forms within macrophages were positive for MIF in symptomatic group. Therefore, it is concluded that MIF plays a favorable role to parasite, mainly in the symptomatic group and this protozoan
possibly exerts immune mimicry, which favors its evasion of host immune system.