Innate Immune System

How does the immune system detect non-self antigens?

Pattern Recognition Receptors (PRRs) detect

• PAMPs (Pathogen-Associated Molecular Patterns)

  • Unique features found in microbes such as bacterial cell walls or viral RNA

• DAMPs (Damage-Associated Molecular Patterns)

  • Signals from damaged or dying cells

After invading antigen enters the cells, what is the first responder cell and what is their two complementary mechanisms to combact?

First responder cell: Neutrophils (part of cellular immunity of II)

Two complementary mechanisms:

• Phagocytosis

• Respiratory burst (increase oxygen consumption)

How does neutrophils carry out phagocytosis? (4)

• Chemotaxis

  • Chemical signals attract neutrophils to site of inflammation

• Attachment

  • Neutrophils and antigen attach to trigger ingestion

  • Use PRRs (pattern recognition receptors) to bind to PAMPs (pathogen associated molecular patterns)

• Phagocytosis

  • Ingestion occurs where pathogen engulfed into phagosome

• Destruction

  • Fuse with lysosomes to produce phagolysosome

  • Digestive enzymes break down pathogen

However what can’t neutrophils do and which cells complete this and how?

Neutrophils lacks: Ability to present Ag to lymphocytes

Antigen presenting is done by: Macrophages

• Marcophages engulf pathogen into vesicle called phagosome

• Phagosome fuses with lysosome forming phagolysosome

• Inside phagolysosome, the pathogen is broken down

• And antigen is presented to T-Cells to start specific adaptive immunity

Following macrophage actions, cytokines are released

• What is the goal

• Which cytokines are released

  • Function

Goal: Recruit and activate immune cells (NK cells, T cells) to enhance inflammation

Which cytokines are released:

• Interleukin-1

  • Function:

    • Induces fever

    • Stimulates T cells (antibody response)

• Interleukin-6

  • Function:

    • Induces fever

    • Stimulates B cells

• Tumor Necrosis Factor-alpha (TNF-α)

  • Function:

    • Induces fever

    • Cytotoxic to antigens

• Interleukin-10

  • Function:

    • Downregulates Th-1 immune response

    • Promotes Th-2 and B cells

• Interleukin-12

  • Function:

    • Stimulates Th-1