A phagocyte is a cell capable of engulfing and destroying other cells, bacteria, and foreign particles, from the Greek phagein, to eat. The professional phagocytes of the immune system, neutrophils, macrophages, and dendritic cells, patrol tissues and blood, recognising pathogens, wrapping them in membrane, and digesting them in internal compartments. This engulfment, phagocytosis, is the immune system’s frontline clearance mechanism and also its cleanup crew, removing dead cells and debris. Nutrition directly supports phagocyte function: protein-energy malnutrition impairs it, while zinc, iron, and vitamins A, C, and D are needed for the cells’ development and killing chemistry. Vaccines work partly by generating antibodies that opsonise pathogens, marking them for faster phagocytic destruction.