Neutrophils, Macrophages and Phagocytosis

• What are the two types of white blood cells?

  Phagocytes and lymphocytes
• What is the role of phagocytes in the immune system?

  They form part of the non-specific defenses
• Which white blood cells are classified as phagocytes?

  Neutrophils and macrophages
• What is the difference between phagocytes and lymphocytes?

  Phagocytes are non-specific; lymphocytes are specific
• What do pathogens like bacteria have on their surface?

  Chemicals not found in humans
• What are opsonans?

  Molecules that tag pathogens as foreign
• What are two types of opsonans?

  Antibodies and complement molecules
• How do opsonans help phagocytes?

  They tag pathogens for recognition and engulfment
• What happens when a phagocyte engulfs a pathogen?

  The pathogen enters a phagosome
• What forms when lysosomes fuse with a phagosome?

  A phagolysosome
• What do lysosomal enzymes do in phagocytosis?

  They break down and destroy the pathogen
• What are antigens?

  Foreign chemicals on the surface of pathogens
• What additional function do macrophages have besides phagocytosis?

  Antigen presentation
• What is the major histocompatibility complex (MHC)?

  Glycoproteins that bind to antigens
• What happens when the MHC binds to antigens?

  It forms an MHC-antigen complex
• What is the role of antigen presenting cells (APCs)?

  They present antigens to lymphocytes
• What do cytokines do when released by phagocytes?

  They signal other immune cells to move
• How can cytokines affect the body during an infection?

  They can trigger inflammation and fever
• What are the stages of phagocytosis?

  1. Pathogen recognition by opsonans
  2. Engulfment of the pathogen into a phagosome
  3. Fusion of lysosomes with the phagosome to form a phagolysosome
  4. Breakdown of the pathogen by lysosomal enzymes
• What are the roles of neutrophils and macrophages?

  • Neutrophils: Rapidly engulf and destroy pathogens
  • Macrophages: Engulf pathogens and present antigens
• What is the role of opsonans in the immune response?

  • Tag pathogens as foreign
  • Facilitate recognition by phagocytes
• What is the significance of cytokines in the immune response?

  • Signal phagocytes and immune cells
  • Trigger inflammation and fever