LE3 .A278 2009

2009

Smith, Todd

Acadia University

Bachelor of Science

Honours

Biology

Biology

An important aspect of innate immunity to Plasmodium falciparum is the phagocytosis of P. falciparum-infected erythrocytes (PEs) by macrophages. Previous studies have revealed that phagocytic efficiencies of macrophages vary greatly between genetically different clones and between infected individuals, and that macrophage function may be inhibited by internalisation of haemozoin, a parasite waste product. The first objective of this study was to assess, in vitro, the influence of parasitaemia, the percentage of infected erythrocytes, on phagocytic efficiency. The second objective was to assess how phagocytic efficiencies during a second challenge (i.e., repeat phagocytosis) were affected by different parasitaemia levels. Macrophages from three human volunteers were incubated with parasite cultures of 0.2%, 1% and 5% parasitaemia levels for 4 h in a phagocytosis assay, and then stained and observed using light microscopy. Four days following the initial phagocytosis assay, macrophages were incubated again with cultures of 0%, 0.2%, 1% and 5% parasitaemia, stained and observed. Macrophages initially incubated with higher parasitaemia levels had significantly increased phagocytic efficiencies, 55.6% for clone ITG-2F6 and 39.8% for clone 3D7A. In macrophages that were initially incubated with 5% parasitaemia, phagocytic efficiency increased by 6 to 7.5 times during the second challenge on day 9 compared to macrophages initially exposed to 0% parasitaemia. These findings reveal that parasitaemia levels in vitro influence the phagocytic efficiency of macrophages and that repeat phagocytosis is not inhibited by parasite internalisation, but that macrophage function is actually increased by prior exposure to infected erythrocytes.

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https://scholar.acadiau.ca/islandora/object/theses:563