Phagocytosis

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PHAGOCYTOSIS Dr AnuPriya J

Transcript of Phagocytosis

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PHAGOCYTOSIS

Dr AnuPriya J

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Scheme

• Definition • Phagocyte – cell types• Steps of phagocytosis• Summary

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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.

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Phagocytes

• The cells performing phagocytosis are called phagocytes.

The cell types are• Neutrophils• Monocytes and• Macrophages

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Steps

1. Margination 2. Diapedesis 3. Chemotaxis 4. Opsonization → attachment stage5. Engulfment stage 6. Secretion (degranulation) stage7. Degradation stage

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Margination

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Diapedesis

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Chemotaxis

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Chemotaxis

Potent chemotactic substances or chemokines are

• Leukotriene B4 (LT-B4)• C5a, C3a• Cytokines

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• 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

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Engulfment stage

Pseudopodia

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Engulfment stage

Phagocyte Lysosome

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Degranulation stage

• Release of lysosomal enzymes into the vesicles

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Degradation stage

• Oxygen dependent bactericidal mechanism mediated by oxidizing agents.

• Oxygen independent bactericidal mechanism mediated by lysosomal enzymes.

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SUMMARY

1. Margination 2. Diapedesis 3. Chemotaxis 4. Opsonization → attachment stage5. Engulfment stage 6. Secretion (degranulation) stage7. Degradation stage

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THANK YOU

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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.