Introduction

The Innate immune system is the body's first barrier of defence to infection. It relies on an older, more generic, and faster acting set of tools than the adaptive system. While the adaptive system is essential for a specific response to infection, it is ultimately the innate system that conquers foreign attackers through means of phagocytosis.

• Non-specific protective mechanisms include such innate factors as:
  • Physical barriers
    • Skin
    • Ciliated mucous membranes
    • Commensal organisms
  • Humoral factors
    • Lysozyme
    • Complement
    • Interferons
  • Cellular mechanisms
    • Phagocytosis
  • Factors which regulate species specificity
    • Membrane receptors for pathogens
    • Nutritional requirements
    • Temperature
    • pH
• Mechanisms of innate immunity are always present and generally unchanging
• Adaptive immunity is acquired only on contact with the infectious agent (antigen) and therefore does not function before first contact with the antigen

Actions of the Innate Immune System

Recognition of Microorganisms

Phagocytosis

Tools of Innate Immunity

Innate Immunity Barriers

Humoral Factors of Innate Immune System

Innate Immunity Cellular Responses

Innate Immunity to Viruses

Innate Immunity to Bacteria

Bacterial responses - B. Catchpole, RVC 2008

The innate response to bacterial infection lies in its first-response role of detection of a foreign organism. By using the above described tools of Pattern-Recognition Receptors (PRRs), the innate response flags up problems while the adaptive response gets itself organized. Once a foreign organism is detected, the innate system responds by engaging in cell warfare via phagocytosis and triggering the inflammatory response. The release of inflammatory cytokines will cause an increase in vasodilation, vascular permeability and an influx of white blood cells. Neutrophils take on their primary role as phagocytes in this phase. In addition, systemic effects of inflammatory cytokines will sustain a rise in core temperature (fever), the release of acute phase proteins from the liver, and bone marrow mobilization as the need for white blood cells production is increased. Acute phase proteins will bind to bacterial cell walls, enhancing neutrophil, macrophage, and complement-initiated phagocytosis.

Interplay of Innate and Adaptive Immunity

Innate Immunity Flashcards

Links

Websites

• http://www.cellsalive.com

References