Ingestion of Giardia lamblia trophozoites by human mononuclear phagocytes.

TitleIngestion of Giardia lamblia trophozoites by human mononuclear phagocytes.
Publication TypeJournal Article
Year of Publication1987
AuthorsHill DR, Pearson RD
JournalInfect Immun
Date Published1987 Dec
KeywordsAnimals, Giardia, Humans, Hydrogen Peroxide, Luminescent Measurements, Macrophages, Microscopy, Electron, Oxygen Consumption, Phagocytosis

Mononuclear phagocytes may be important effector cells against Giardia lamblia. Human monocyte-derived macrophages were incubated with G. lamblia trophozoites in 13% heat-inactivated autologous serum. At a G. lamblia/macrophage ratio of 1:1, the number of trophozoites ingested per 100 macrophages ranged from 1 to 12 at 0.5 h and increased for all donors (n = 6) to 10 to 92 at 8 h. Ingestion was confirmed by electron microscopy. Increasing the parasite/phagocyte ratio to 5:1 increased the percentage of macrophages with adherent but not ingested trophozoites. Incubating Giardia cells and macrophages with 20% immune serum increased ingestion of parasites eightfold, indicating that anti-G. lamblia antibody can enhance ingestion. Both phase-contrast microscopy and electron microscopy documented trophozoite destruction within macrophages. Ingestion of parasites elicited an oxidative burst as measured by luminol-enhanced chemiluminescence. In vitro, Giardia trophozoites were killed by greater than or equal to 5 X 10(-5) M H2O2. Fusion of lysosomes with parasite-containing phagosomes was suggested by acridine orange-stained preparations. Human macrophages have the capacity to ingest Giardia trophozoites and to kill intracellular parasites, possibly by oxidative microbicidal mechanisms.

Alternate JournalInfect. Immun.
PubMed ID3679547