CHAPTER 24 The Immune System

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CHAPTER 24The Immune System
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Pathogens

• Disease causing agents such as bacteria, viruses,
  fungi, protozoans, and other parasites. ( NOT all
  microorganisms are pathogens)

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Transmission of disease

• Pathogens can be transmitted to a host from
  reservoirs in four main ways by direct contact,
  by an object, through the air, or by an
  intermediate organism called a vector.

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Immune System

• Bodies primary defense against pathogens
• Three cooperative lines of defense have evolved
  to counter these threats.
• Two of these are nonspecific - that is, they do
  not distinguish one infectious agent from
  another.

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1st line Physical Barriers

• non-specific defense
• external barriers
• skin mucus membranes
• excretions
• sweat
• stomach acid
• tears
• mucus
• saliva
• lick your wounds

Lining of trachea ciliated cells mucus
secreting cells
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2nd Generalist, broad range patrols

• Patrolling white blood cells
• attack invaders that get through the skin
• recognize invader by reading antigen
• surface name tag
• phagocyte cells
• macrophages
• big eaters

Macrophage eating bacteria
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Lymph system
Production of white blood cells traps foreign
invaders
lymph vessels (intertwined amongst blood vessels)
2nd circulatory system
lymph node
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The lymphatic system becomes a crucial
battleground during infection

• a network of lymphatic vessels and organs
• It returns tissue fluid to the circulatory system
• It fights infections
• Lymph nodes are key sites for fighting infection
• They are packed with lymphocytes and macrophages

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Phagocytes

• Macrophages wander in the interstitial fluid
• They eat any bacteria and virus-infected cells
  they encounter

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Phagocytes
macrophage
bacteria
white blood cells that eat
macrophage
yeast
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Antimicrobial Proteins

• Interferons acts in warning other cells of a
  viral invasion
• Complement help attract phagocytes to foreign
  cells and help destroy foreign cells

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Natural Killer cells

• A type of white blood cell that destroy the
  body's own infected cells, may attack cells that
  form tumors

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The inflammatory response mobilizes nonspecific
defense forces

• Tissue damage triggers the inflammatory response
  (redness, swelling, warmth, pus) injured cells
  release chemical signals
• histamines
• increases blood flow
• brings more white blood cells to fight bacteria
• brings more red blood cells clotting factors to
  repair
• The inflammatory response can
• disinfect tissues
• limit further infection

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Fever

• When a local response is not enough
• full body response to infection
• raises body temperature
• higher temperature helps in defense
• slows growth of germs
• helps macrophages
• speeds up repair of tissues

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SPECIFIC IMMUNITY 3rd line of defense

• IMMUNE RESPONSE
• a recognition system that distinguishes self
  from non-self
• responds to foreign molecules called antigens
• Stimulates the body to make antibodies
• specific defensive proteins which help to
  counter antigens in various ways

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How are invaders recognized?

• Antigens
• chemical name tags on the surface of every cell
• self vs. invader

disease-causingbacteria
disease-causingvirus
one of yourown cells
antigens sayI am an invader
antigens sayI belong here
antigens sayI am an invader
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Immunityprotection afforded to an organism by
previous exposure to an antigen

• 2 types
• Active long term, conferred by actual encounter
  with infection (naturally acquired) or
  vaccination (artificially acquired)
• vaccine substance consisting of
  weakened, dead, ,or parts of pathogen or antigen
  that when injected , stimulates the immune system

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Immunity

• 2. Passive short term, antibodies passed on, not
  stimulated by antigens,
• acquired naturally by placenta or breast milk or
  artificially acquired by a shot

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Immune Response 3rd line of defense

• Governed by 2 different parts of the immune
  system
• 1. Humoral Immunity results in the production of
  antibodies
• 2. Cell-mediated Immunity defensive activities
  are carried out by specialized cells circulating
  around the body

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Lymphocytes type of white blood cell that carry
out the immune response
B lymphocyte

• Two kinds
• B cells secrete antibodies that attack antigens
  (humoral immunity)
• T cells attack cells infected with pathogens
  (cell-mediated immunity)

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The initial immune response results in a type of
memory

• primary immune response produces memory cells
• These cells may confer lifelong immunity
• When memory cells are activated by subsequent
  exposure to an antigen, they mount a more rapid
  and massive secondary immune response

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Humoral Immune Response

• Triggered by a specific antigen, a B cell
  differentiates into a plasma cell
• -The plasma cell secretes antibodies

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Antibodies are the weapons of humoral immunity

• An antibody molecule has antigen-binding sites
  specific to the antigen
• Do not posses the power to destroy antigens
  directly, tag and mark them for destruction by a
  variety of mechanisms

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B cells antibodies

• B cells
• white blood cells that attack invaders in blood
• mature in Bone marrow
• Patrolling B cells
• make antibodies against invader immediately
• Memory B cells
• remembers invader
• can make antibodies quickly the next time
• protects you from getting disease more than once

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B cells immune response
invader(foreign antigen)
recognition
10 to 17 days
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What if the attacker gets past the B cells in
the blood infects some of your cells?

• You need trained assassins to kill off these
  infected cells!

Attackof the Killer T cells!
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T cells

• T cells mature in Thymus
• Helper T cells
• sound the alarm for rest of immune system
• Cytoxic or Killer T cells
• destroy infected body cells
• Memory T cells
• remembers invader reacts against it again
  quickly

Wheres that?
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Cell-Mediated Immunity

• An antigen-presenting cell (APC) first displays a
  foreign antigen and one of the bodys own self
  proteins to a helper T cell
• The helper T cells receptors recognize the
  self-nonself complexes on the APC
• - The interaction activates the helper T
  cells
• The helper T cell can then activate cytotoxic T
  cells with the same receptors
• Helper T cells also stimulate the humoral
  responses
• Cytotoxic T cells( or Killer T cells) bind to
  infected body cells and destroy them

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Attack of the Killer T cells

• Killer T cells destroy infected body cells
• T cell binds to invaded cell
• secretes perforating protein
• punctures cell membrane of infected cell
• cell bursts

Killer T cell
vesicle
Perforin puncturescell membrane
cell membrane
cell membrane
invaded cell
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Cytotoxic T cells (Killer T) may help prevent
cancer

• The surface molecules of cancer cells are altered
  by the disease

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Immune response
invader
skin
skin
invaders in body
invaders in blood
invaders infect cells
macrophages
helperT cells
B cells
T cells
patrollingB cells
memoryB cells
memoryT cells
killerT cells
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The immune system depends on our molecular
fingerprints

• Self is signaled by major histocompatibility
  complex (MHC), a group of proteins unique to the
  individual that is present on the surface of
  cells
• Can cause rejection of transplanted organs

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DISORDERS OF THE IMMUNE SYSTEM
Rheumatoid arthritis

• Autoimmune diseases
• The system turns against the bodys own molecules
  
• Examples Rheumatic fever, Type I Diabetes,
  Multiple Sclerosis, Rheumatoid arthritis, Lupus

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DISORDERS OF THE IMMUNE SYSTEM
HIV on a lymphocyte

• Immunodeficiency diseases
• Immune components are lacking, and infections
  recur
• Ex Acquired immune deficiency syndrome (AIDS)
• SCIDS

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AIDS

• HIV (Human Immunodeficiency Virus) the virus
  that causes AIDS
• HIV is transmitted mainly in blood and semen
• HIV kills helper T-cells and leads to AIDS

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DISORDERS OF THE IMMUNE SYSTEM

• Allergies are overreactions to certain
  environmental antigens called
• allergens Ex. Animal dander, dust mites,
  pollen
• release of histamine causes symptoms
• Antihistamines can relieve symptoms
• anaphylactic shock life threatening reaction to
  injected or ingested allergens.