Phagocytosis
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Transcript of Phagocytosis
PHAGOCYTOSIS
Dr AnuPriya J
Scheme
• Definition • Phagocyte – cell types• Steps of phagocytosis• Summary
Phagocytosis
• Phagein = "to devour", kytos = "cell“, osis = “process” (from Ancient Greek)
• Phagocytosis is the process of engulfment and destruction of solid particles such as bacteria, dead tissue and foreign particles by the cells.
Phagocytes
• The cells performing phagocytosis are called phagocytes.
The cell types are• Neutrophils• Monocytes and• Macrophages
Steps
1. Margination 2. Diapedesis 3. Chemotaxis 4. Opsonization → attachment stage5. Engulfment stage 6. Secretion (degranulation) stage7. Degradation stage
Margination
Diapedesis
Chemotaxis
Chemotaxis
Potent chemotactic substances or chemokines are
• Leukotriene B4 (LT-B4)• C5a, C3a• Cytokines
• Opsonization refers to the process of coating of bacteria by the opsonins.
• The opsonin coated bacteria gets attached to the surface of phagocyte through the opsonin receptors.
• The principal opsonins are IgG opsonin and C3b opsonin.
Opsonization → Attachment stage
Engulfment stage
Pseudopodia
Engulfment stage
Phagocyte Lysosome
Degranulation stage
• Release of lysosomal enzymes into the vesicles
Degradation stage
• Oxygen dependent bactericidal mechanism mediated by oxidizing agents.
• Oxygen independent bactericidal mechanism mediated by lysosomal enzymes.
SUMMARY
1. Margination 2. Diapedesis 3. Chemotaxis 4. Opsonization → attachment stage5. Engulfment stage 6. Secretion (degranulation) stage7. Degradation stage
THANK YOU
Engulfment
• Formation of cytoplasmic pseudopods by the phagocytes around the bacteria.
• The bacteria is endocytosed and is contained in a vesicle thus forming a phagosome
• The phagosome fuses with nearby lysosome to form phagolysosome.