Phagocytosis Process

Phagocyte Attraction

• Phagocytes are drawn to areas of invasion by:

  • Chemical products released by the microorganism.

  • Phospholipids from injured mammalian cells.

  • Components of the complement system.

• The phagocyte enters the area and attaches to the microorganism.

Phagocyte Attachment

• Attachment is facilitated by surface receptors, including:

  • Antibodies

  • Lipopolysaccharides

  • Complement receptors

• Example: $C3b$$$C3b$$ component of complement coats bacteria or particles and binds to $C3b$$$C3b$$ receptors on the phagocyte.

Opsonization

• Opsonization is the process of coating to enhance phagocytosis.

Engulfment and Phagosome Formation

• The microorganism is engulfed by the phagocyte into a vacuole called a phagosome.

Phagolysosome Formation

• Lysosomes (vesicles in the cytoplasm) fuse with the phagosome.

• This fusion releases digestive enzymes such as lysozyme and proteases into the phagosome.

• The resulting structure is called a phagolysosome.

Digestion and Exocytosis

• Inside the phagolysosome, microorganisms are killed and digested.

• The digested contents are eliminated from the phagocyte by exocytosis.