The Immune System

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The Immune System

• Packet 22
• Chapter 31

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Introduction

• The immune system includes all of the structures
  and processes that provide a defense against
  potential pathogens (disease causing agents).
• Immunity, the ability of an organism to resist
  disease, are in two forms
• Passive Immunity
• Immunity passed from mother to child
• Via genes
• There is no immune response
• Active Immunity
• The body produces a response to a particular
  pathogen.

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Active Immunity

• Human Body Defense Mechanisms

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Human Body Defense Systems

• Defense Mechanisms
• Non-Specific
• Defense is a rapid response to a wide range of
  pathogens
• Specific
• Takes several days to mount
• Delivered by the Immune System
• Lymphocytes

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Lymphocytes
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Introduction

• Lymphocytes (a type of white blood cell) are
  derived from unspecialized stem cells in the bone
  marrow.
• Large numbers of lymphocytes are found in the
  thymus, spleen and lymph nodes.
• There are two types of lymphocytes
• T cells
• Thymus-dependent lymphocytes
• B cells
• Derived from the discovery of B cells in the
  bursa of Fabricius
• Mammals do not have this organ

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B Cells

• Secrete antibodies (proteins) into the blood and
  lymph in order to inactivate pathogens.
• Combat bacterial infections and some viral
  infections
• Because blood and lymph are body fluids (humors),
  and since they release antibodies, the B cells
  are said to provide humeral immunity
  (antibody-mediated immunity)

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T Cells

• Attack host cells that have become infected with
  viruses or fungi, transplanted human cells and/or
  cancerous cells.
• These cells do not secrete antibodies.
• Must be in close proximity to destroy the
  infected cell.
• Provide cell-mediated immunity.
• Cell-mediated immunity involves the use of T
  cells.

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Humoral Immuntiy vs. Cell-Mediated Immunity

• See Pages 764 765 in textbook.

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Specific Mechanisms
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Specific Defense Mechanisms

• Antigens
• Molecules (proteins), found on the surface of
  cells, that stimulate the production of specific
  antibodies.
• The ID card.
• Natural
• Foreign
• Haptens
• Small organic molecules that can become antigens
  if they are bond to proteins.
• Immunoassays

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Non-Specific Mechanisms/Barriers
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Non-Specific Defense Mechanisms

• Phagocytosis
• Engulfing of pathogens
• Neutrophils
• Macrophages
• Phagocytes
• Fever
• Produced by cytokines
• High fevers are dangerous however fevers aid in
  the destruction of pathogens
• Interferons
• Polypeptides that act as messengers that protect
  other cells in the vicinity from viral infection.

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Introduction

• The non-specific defense systems utilizes
  different defensive lines in order to be
  successful.
• Similar to having an alarm system for the house
  but there are specific sensors, at the doors and
  windows for example, that trigger the alarm
  system.

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The Immune SystemNon-Specific Defense System
Barriers/MechanismsThe First Line of Defense

• The Skin
• Mucous Membranes
• Cilia
• Lines the lungs
• Gastric Juice
• In the stomach
• Kills most microbes

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The Immune SystemNon-Specific Defense
Barriers/MechanismsThe Second Line of Defense

• Second Line of Defense
• Inflammatory Response
• Redness swelling heat pain
• Lymphocytes are activated.
• Fever is developed.

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The Immune SystemNon-Specific Barriers/Mechanisms
The Third Line of Defense

• Third Line of Defense
• Consists of mechanisms and agents that target
  specific antigens
• Via the use of lymphocytes.

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Over Active Immune System
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Allergies

• An allergy is an oversensitivity to a normally
  harmless antigen.
• Harmless antigens, that cause the over-the-top
  response, are known as allergens.
• Food
• Peanuts
• Airborne
• Pollen
• Pet dander
• Mold
• Chemical
• Penicillin
• Jewelry metals

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Review