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 component of complement coats bacteria or particles and binds to 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.