Conference presentation delivered at the 15th <a href="http://www.aegeanconferences.org/src/App/conferences">Aegean Innate Immunity Conference (Chania, Crete, Greece, 2018)</a>.
<p>Phagocytosis is a fundamental cellular activity preserved in a broad spectrum of eukaryotic organisms, from simple unicellular protists where it is used for the ingestion of food particles, to complex multicellular organisms where phagocytosis is an essential component of innate immunity against invading microorganisms. In this study, we report on the effect of glucose on phagocytosis in the model protist Tetrahymena pyriformis. Initial experiments examined the effects of temperature and contact time with the phagocytic target India ink, on phagocytosis by Tetrahymena. Phagocytosis was assessed by counting the number of phagocytic vacuoles in cells fixed with glutaraldehyde and visualized by light microscopy. Phagocytosis was maximal at room temperature and after 30 min of incubation with India ink. Glucose suppressed phagocytosis in a concentration-dependent manner. In addition, we demonstrated that exposure of cells to other hypertonic solutions, including sucrose, fructose, galactose and mannitol, used at 25mM concentrations, respectively, suppressed phagocytosis. Furthermore, we showed that hypotonic conditions, including incubation of cells in distilled water or diluted proteose peptone culture medium, had little effect on phagocytosis of India ink by Tetrahymena. Our studies may be relevant in elucidating the role of glucose and/or hypertonicity in contributing to impaired phagocytosis, and possibly enhanced risk of infections, in patients with untreated or poorly controlled diabetes mellitus, a condition associated with hyperglycemia.</p>
