9.1.4 Phagocytosis(Small Particle Disease) 9. 1.4.1 Primary*Phagocytic Cells(Fig. 9.3) Polymorphonuclear neutrophils(PMn) Macrophages(Figs. 9.4 and 9.5) Multinucleated foreign body giant cells( Figs. 9.3 and 9.5) *Other cells such as fibroblasts may be phagocytic under special circumstances 9. 1.4.2 Stages of Phagocytosis a)Contact b)Binding membrane receptor binding c) Formation of Phagosome infolding of the cell membrane engulfing the particle membrane-bound compartment containing the particle d) Formation of Phagolysosome fusion of lysosome(membrane-bound packet of enzyme and other degradative agents) with the phagosome 9. 1.4.3 Degradative and Inflammatory Regulators released by the macrophage During Ph agocytosis Oxygen-derived free radicals Eicosanoids prostaglandins leukotrienes Cyt tumor necrosis factor interleukins 9. 1.4.4 Mechanisms of Release of Products from the Macrophage Cell death Regurgitation Perforation/Cell Wounding endocytosis 9. 1.4.5 Chemotactic Stimuli for Monocytes Chemotactic peptides(bacteria) Leukotriene b Lymphokines(cytokines from lymphocytes th factors(. g, PDGF Collagen and fibronectin(fragments) Fragments of complement molecules (viz., C5a)9.1.4 Phagocytosis (Small Particle Disease) 9.1.4.1 Primary* Phagocytic Cells (Fig. 9.3) Polymorphonuclear neutrophils (PMN) Macrophages (Figs. 9.4 and 9.5) Multinucleated foreign body giant cells (Figs. 9.3 and 9.5) *Other cells such as fibroblasts may be phagocytic under special circumstances 9.1.4.2 Stages of Phagocytosis a) Contact b) Binding - membrane receptor binding c) Formation of Phagosome - infolding of the cell membrane engulfing the particle - membrane-bound compartment containing the particle d) Formation of Phagolysosome - fusion of lysosome (membrane-bound packet of enzyme and other degradative agents) with the phagosome 9.1.4.3 Degradative and Inflammatory Regulators Released by the Macrophage During Phagocytosis Degradative Agents - Lysosomal enzymes - Oxygen–derived free radicals Regulators Eicosanoids - prostaglandins - leukotrienes Cytokines – tumor necrosis factor – interleukins 9.1.4.4 Mechanisms of Release of Products from the Macrophage Cell death Regurgitation Perforation/Cell Wounding Reverse endocytosis 9.1.4.5 Chemotactic Stimuli for Monocytes Chemotactic peptides (bacteria) Leukotriene B4 Lymphokines (cytokines from lymphocytes) Growth factors (e.g., PDGF, TGF- ) Collagen and fibronectin (fragments) Fragments of complement molecules (viz., C5a)