Early interactions ofEntamoeba histolyticatrophozoites with parenchymal and inflammatory cells in the hamster liver: an immunocytochemical study

Abstract

We studied the early in situ interactions of live and fixed Entamoeba histolytica trophozoites with hamster hepatic parenchymal and inflammatory cells using immunoperoxidase and immunoelectronmicroscopy. Close contact between trophozoites and endothelial cells and the diffusion of amoebic molecules from trophozoites towards nearby endothelial cells and distant hepatocytes were observed. The inflammatory cells around the amoebae and the remnants of parenchymal cells and hepatocytes located close to the lesion had a positive stain for amoebic molecules. In the amoebae, at the ultrastructural level, molecules were attached to the membranes and inside the vesicles. These molecules were apparently released into the space formed between the parasite and the endothelial cells. The endothelial cells and the nearby and distant hepatocytes captured amoebic molecules, and later they became necrotic. Contrarily, when fixed amoebae were inoculated, amoebic molecules were captured by endothelial cells and polymorphonuclear (PMN) leukocytes, but neither suffered any damage. In this work, we are presenting evidence clearly showing that some molecules of the amoeba can diffuse away long distances causing cytotoxic effects and even necrosis on hepatic cells of hamster liver without the need of the trophozoite being in close contact with the target cells. They also may promote lytic or proinflammatory effects by inducing the secretion of enzymes or cytokines in other nonparenchymal cells, like PMN leukocytes and endothelial cells. Our results suggest that the accepted mechanisms of cytotoxicity by amoebae are not exclusively restricted to the following sequence: adhesion, phagocytosis, and necrosis.

Trophozoites of Entamoeba histolytica express a CD59-like molecule in human colon

“…Then, they were washed in PBS for 5 min and incubated in 20% fetal bovine serum (Hyclone) in PBS for 30 min and then washed three times with 0.025% PBS-tween for 10 min. The slides of infected and uninfected tissue were incubated with the primary antibody for 12 h using the following dilutions: 1:500 rabbit anti-E. histolytica immune serum raised in our laboratory (Ventura-Juárez et al 2002) and 1:100 mouse anti-human CD59 monoclonal antibody (Chemicon international CBL467 suitable for immunohistochemistry). All slides were washed with 0.025% PBS-tween for 10 min.…”

Vagotomy Induces Deregulation of the Inflammatory Response during the Development of Amoebic Liver Abscess in Hamsters

“…Tsutsumi et al [24] and Ventura-Juarez et al [53] showed that E. histolytica trophozoites are capable of inducing an important inflammatory response via polymorphonuclear and mononuclear leukocytes in hamsters. Pacheco-Yepez et al [54] demonstrated, through immunohistochemistry and PCR techniques, that the immune response to E. histolytica invasion includes a gradual increase in TNF-α, IFN-γ, IL-8, and IL-1β during the early stages (the first 3 h) of ALA development.…”

Amebic cysteine proteinase 2 (EhCP2) plays either a minor or no role in tissue damage in acute experimental amebic liver abscess in hamsters

“…In vitro experiments show that amebas secrete proteases into the culture medium (Leippe et al 1995;Reed and Gigli 1990;Serrano et al 1996) and it is suggested that such proteases are responsible, at least in part, for the extensive tissue destruction characteristic of the disease. Using a polyclonal antibody raised against whole amebic extracts, Ventura-Jua´rez et al (1997) stained immunohistochemically early experimental amebic lesions and showed that not only were trophozoites positive but also that there was diffusion of positive material in the vicinity of amebas. Using a polyclonal antibody antiEhCP1, Stanley et al (1995) were able to stain amebic trophozoites in acute experimental liver abscesses produced in SCID mice; and they claim to have detected positive staining in the tissues near the parasites.…”