The Immune System

1
The Immune System

• Ch. 24

2
Objectives Define and Comprehend

• Nonspecific vs. specific immunity responses
• Different types of nonspecific responses
• Humoral vs. cell-mediated immunity

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Nonspecific vs. specific defenses

• Nonspecific defenses do not distinguish one
  infectious microbe from another
• Specific defenses recognize and defend against
  invading microbes and cancer cells

4
1 minute brain storm

• What is an immune system?
• What are the components of an immune system?

5
Nonspecific defenses

• Skin is a barrier that most bacteria and viruses
  cant penetrate
• Acids secreted by skin prohibit growth of many
  microbes
• Sweat, saliva, and tears contain enzymes that
  attack bacterial cell walls
• Mucus produced in digestive and respiratory
  systems also protects against microbes

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Nonspecific defenses

• Microbes that penetrate skin, digestive, or
  respiratory systems face neutrophils and
  monocytes
• macrophages that eat bacteria and viruses
• Interferons and complement proteins attack
  microbes either directly or indirectly by
  impeding their reproduction

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Nonspecific defenses

• Interferons are produced by infected cells
• Diffuse to healthy cells where they cause the
  cell to inhibit viral production
• Complement proteins are activated by microbes or
  immune system
• Coat infected cells easier to eat
• Can amplify inflammatory response

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Nonspecific defenses inflammatory response
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Nonspecific defenses inflammatory response

• Redness, heat, and swelling caused by
• Increase in blood flow, fluid, and cells
• Inflammatory response disinfects and cleans
  injured tissues
• Pus dead white cells and fluid
• Systemic response is widespread
• Toxins or microorganisms released in bloodstream
• Circulates through body

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Nonspecific defenses inflammatory response

• Systemic response contd.
• Inflammatory weapons increase white blood cells,
  fever
• Low-grade fever can stimulate phagocytosis and
  inhibit growth of many microorganisms

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Lymphatic system
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Lymphatic system

• Involved in both specific and nonspecific
  responses
• Lymphatic system defenses occur in lymph nodes
  and lymphatic system organs
• Packed with lymphocytes and macrophages
• Lymph carries microbes from infection sites and
  some cancer cells
• In the lymphatic organs, macrophages may eat
  the invaders (nonspecific)
• Lymphocytes can be involved in specific immune
  response

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Lymphatic system

• Why do your lymph nodes swell when you are
  fighting certain kinds of infections?
• Production of lymphocytes in nodes

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IN PAIRS in your notebook

• Describe the types of nonspecific responses your
  body has at its disposal if it were to be
• Invaded by a microbe
• Cut

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Specific immunity

• Often more effective than nonspecific response
• It also amplifies nonspecific response
• Specific response begins due to presence of an
  antigen
• Can either increase number of cells that attack
  invader directly OR
• Produce antibodies
• Immune system remembers antigens it has
  previously encountered
• Responds immediately and vigorously
• Is adaptive

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Specific Immunity

• Vaccines D\Vaccines\Vaccines.mpg

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Objectives Define Comprehend

• Role of clonal selection in immunity response
• Primary vs. secondary response
• Antibodies
• T cells
• Autoimmune vs. immunodeficiency diseases
• Allergies
• HIV/AIDS

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Lymphocytes
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Specific Immunity Lymphocytes

• Humoral system defends against bacteria and
  viruses present in body fluids
• Fluids blood, lymph, and interstitial fluid
• Antibodies, secreted by B cells and dissolved in
  the blood, are carried in lymph and blood to
  sites of infections
• Cell-mediated immunity
• T-cells circulate in blood and lymph
• Attack body cells that have been infected

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Specific Immunity Lymphocytes

• For BOTH humoral and cell-mediated immunity
• B T cells have antigen receptors (antibodies)
  that protrude from cell surface
• specific for one type of antigen
• Each person has between 100 million to 100
  billion different kinds of B T cells!

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Antigens

• Most antigens are molecules that are present on
  viral surfaces or foreign cells
• B cells respond to free antigens in body fluid
• Different antibodies can bind to the same antigen

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Specific immunity clonal selection
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Primary vs. Secondary immune response
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Question

• Why are childhood diseases referred to as such?
• First exposure occurs during childhood, which
  then confers immunity during remaining years of
  the individuals life

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How do antibodies block invaders?

• Antibodies bond to antigen molecules, which marks
  them and results in either
• An increase in the possibility of phagocytosis
• Activation of complement proteins that can cause
  the invaders cell to rupture
• D\ImageLibrary16-26\24-TheImmuneSystem\24-11-Anti
  bodiesAnim.mov

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Role of T cells in Immunity

• T cells battle pathogens that have already
  entered body cells
• Respond to antigens that have bonded to body cell
  surfaces
• Mount cell-mediated defense and aid humoral
  immunity

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T cells

• Cytotoxic T cells
• Only T cells that kill other cells
• Synthesize a protein that ruptures infected cell
• Helper T cells
• Secrete stimulatory proteins that help
• Promote production of more helper T cells and
  memory cells
• Activate cytotoxic T cells
• Stimulate B cells to produce antibodies

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Question

• Why is it important that our immune system can
  distinguish self from nonself?
• Cell identification tags enable immune system to
  determine the difference

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Autoimmune Diseases

• MS T cells attack myelin a protein that
  insulates the axons of neurons (a brain thing)
• Most common chronic neurological disease in
  developed countries

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Immunodeficiency diseases

• SCID (Severe Combined Immunodeficiency) T and/or
  B cells are absent or inactive
• bubble people

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Allergies
Stage 1
Stage 2
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HIV/AIDS

• HIV destroys the immune system by infecting
  helper T cells
• Eventually develop AIDS
• Body cannot carry out cell-mediated or humoral
  response
• Die from opportunistic infections
• 36.1 million people have HIV/AIDS
• 5.3 million new cases each year

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Class Problem

• Describe what happens when you get the flu
• The first time
• The second time
• Include everything