Phagocytic

• Phagocytic Cells: Neutrophils (70% of leukocytes) - purely phagocytic and Monocytes (5% of leukocytes) - become macrophages when they leave the blood and migrate to tissues
• Macrophages have multiple roles: Phagocytose microbes, digest dead neutrophils and damaged body cells, and act as antigen-presenting cells (APC) for T an B) cell activation - they are long lived
• Phagocytosis


  When a pathogen enters, it is recognised as non-self by specific antigens in its membrane; non-specific proteins (complement) or specific anti bodies, reduced by B-lymphocytes circulate in blood and bind to them (Opsonisation)
• Phagocytosis


  1. After opsonins phagocytes engulf pathogen by endocytosis, it’s in a vesicle called a phagosome; lysosomes fuse with its membrane, to form a phagolysosome and hydrolytic enzyme (lysins and lysozyme) are released

  3. The lysins digest the large molecules of the pathogen, releasing smaller nutrients into the phagocytes

  4. The useful reduces of digestion are transported into the cytoplasm of the phagocytes by simple diffusion, facilitated diffusion or active transport
• Antigens


  From the pathogen are then attached to a specific receptor (MHC) and presented on the cell surface of the phagocytes in order to activate T and B Cells
• Opsonins: Phagocytes have receptor proteins within their plasma membranes that attach to the complement proteins or antibodies on the pathogen