Phagocytosis of Giardia lamblia trophozoites by human colostral leukocytes

Aim: To determine the phagocytic activity of the polymorphonuclear and mononuclear cells present in human colostrum, and to verify the influence of opsonins in the adherence, ingestion and killing of Giardia lamblia trophozoites. Methods: Polymorphonuclear and mononuclear phagocytes were incubated with G. lamblia trophozoites, in the presence as well as the absence of supernatant of human colostrum (the source of opsonins) for 30, 60 and 120 min. The trophozoites/phagocytes ratio was 1:1, and the percentage of phagocytosed trophozoites was determined by microscopic examination of acridine orange-stained cells. Results: The mononuclear phagocytes presented more functional activity than the polymorphonuclear. The highest indexes of adherence (77.6 +/- 5.1), ingestion (68.9 +/- 5.5) and killing (48.5 +/- 4.9) were obtained through the incubation of mononuclear cells in the presence of colostrum supernatant for 120 min. Conclusion: The phagocytes of human colostrum were able to ingest G. lamblia trophozoites and presented microbicidal activity in vitro, suggesting that these phagocytes may act as an additional mechanism of protection against infant giardiasis through breastfeeding.