Phagocytosis is one main mechanisms of the non-specific immune defence and one of the first processes responding to infection.Although most cells are capable of phagocytosis, some cell types perform it as part of their main function. These are called 'professional phagocytes.'Neutrophils, macrophages, monocytes and dendritic cells are professional phagocytes.Neutrophils patrol the bloodstream and rapidly migrate to the infected tissues in large numbers.Monocytes, and the macrophages that mature from them, and dendritic cells leave blood circulation to be resident in tissues.Receptors recognise bound IgG antibodies or pathogen-associated molecular patterns.This leads to the protrusion of the cell membrane to engulf the pathogen.The phagosome is the organelle formed. It is fused with lysosomes, forming a phagolysosome.The phagolysosome is acidified, activating degradative enzymes. The ingested material is then digested in the phagolysosome.Neutrophils kill the pathogens. Macrophages and dendritic cells combine antigens from the pathogen with proteins called the major histocompatibility complex and move them to the cell surface to become antigen-presenting cells.