Immune System

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Immune System

• Not truly a system but many factors working
  together.

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1. Function

• Protection from disease causing agents (pathogens)

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Pathogens

• Viruses
• Nonliving
• No response to antibodies
• No nutrients needed
• Cannot reproduce without taking over a specific
  cell
• DNA or RNA

• Bacteria
• Living
• Antibodies can kill
• Need energy, water
• Reproduce on own
• DNA and RNA

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These are red and white blood cells.
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2. Non-specific defenses kill anything

• Skin oils, sweat, waxes kill bacteria
• Good bacteria kill bad.
• Mucous/hairs catch the bad stuff

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Continued

• digestive enzymes kill some in the stomach
• white blood cells (neutrophils and macrophages
  engulf bacteria and viruses)
• Interferon stops reproduction of viruses

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macrophage shown engulfing three cancer cells.
Macrophages are specialized white blood cells or
leukocytes that circulate through the blood
stream searching for bacteria, dead or abnormal
cells, or foreign objects to engulf. SEM X3000.
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phagocytosis
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• Fever Helps your body fight infection.

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3. Major parts of immune system

• Bone marrow makes the new white blood cells
  (also called lymphocytes)
• B cells mature in the bone marrow
• T cells mature in the Thymus gland
• Spleen filters pathogens from the blood

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4. Immune Response

• The lymphocytes launch an attack of a pathogen
• The substance that provokes the attack is called
  an antigen
• Many things can be an antigen such as pollen, bee
  stings, toxins, or markers on foreign cells

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Two types of immune Responses

• Cell Mediated-involves T cells
• Humoral- involves B cells

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5. Beginning steps in any of the two kinds of
immune response

• A macrophage engulfs and destroys a pathogen
• Fragments of the pathogens antigens are
  displayed on the surface of the macrophages cell
  membrane
• Macrophage releases interleukin-1
• Helper T cell is triggered to release
  interleukin-2

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6a. Cell-mediated response

• interleukin-2 stimulates the helper T cells,
  cytotoxic T cells, and suppressor T cells to
  rapidly divide
• Cytotoxic T cells destroy any of the bodys cells
  that have been infected by the pathogen

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• c. Suppressor T cells help to shut down the
  immune response after the pathogen has been
  cleared from the body

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6b. Humoral Immune Response

• Interleukin-2 and antigen presentation of a
  macrophage or a T cell causes B cells to divide
  and differentiate into plasma cells
• Plasma cells secrete defensive proteins into the
  blood called antibodies
• Antibodies are Y-shaped molecules that have two
  identical arms.

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• d. Each arm can hook to a specific antigen
• e. Antibodies inactivate the pathogens or trigger
  its destruction by other defenses

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7. Primary Immune Response

• The first time the body encounters an antigens is
  called the primary immune response
• After the infection, most immune cells die but
  some B cells and T cells remain
• They are called memory cells

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8. Secondary response

• secondary infection from the same pathogen
• Memory B and T cells act quickly against the
  known pathogen

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9. Allergies

• B lymphocytes are producing antibodies against
  nonpathogenic things like fur, pollen, food, and
  other allergens.
• Histamine is releasedsneezing, itching, watering
  eyes, etc.

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10. Immunity

• Acquired
• Developed after birth
• Vaccinationexposing a person to killed or
  weakened pathogens
• Primary immune response is activated

• Natural
• Present at birth

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11. AIDS

• Enters blood, engulfed by phagocyte, enters a
  helper T cell,
• May be dormant in helper T cell for up to 10
  years
• At some point it reproduces and takes over more
  cells
• Helper T cells are killed as virus bursts out
• Suppressed immune response

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colored scanning electron micrograph of a T4 cell
(green) infected with HIV (red).