Phagocytosis: Enhancement

AbstractPhagocytosis is the process of engulfment of particles by phagocytic cells, such as macrophages and neutrophils. The ingestion of pathogens, tissue debris or apoptotic cells by these cells may be enhanced by coating the particle with host molecules called opsonins, which allow the recognition and subsequent ingestion of the particles by phagocytic receptors. There are numerous opsonins, including complement‐derived proteins such as iC3b and immunoglobulin G, which are recognized by specialized receptors including complement receptor type 3 and FcγR. The failure of efficient uptake of particles and apoptotic cell debris can have deleterious effects on the host such as leading to the spread of infection and the generation of autoimmune conditions, such as systemic lupus erythematosus.Key concepts:Efficient removal of particulate matter by phagocytic cells requires direct recognition of the particle by the cell along with indirect binding via host‐derived molecules known as opsonins.Enhanced phagocytic uptake of pathogens and dying cells is mediated by a number of overlapping opsonins and phagocytic receptors.Ingested particles are recognized by a number of different receptors which may cooperate with each other to modulate their function/activity.Though multiple receptors can mediate phagocytosis, there are subtle differences in their signalling and cell biology that can result in different cellular outcomes downstream of uptake.Defects in the removal of both pathogens and apoptotic cells can lead to increased susceptibility to infection and autoimmune diseases.