Immune System

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Immune System
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A Boo Boo lets in germs
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LikeBacteria
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Or a virus
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A germ is still a germ.

• Pathogenagent that causes disease
• 2. Antigen foreign particle that triggers an
• immune response
• - often they are proteins on the surface
  of viruses and bacteria

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Your Bodys Defenses AgainstDisease

• Nonspecific Defenses Attack all pathogens and
  antigens the same way
• Specific Defenses Immune Response Attack
  pathogens that get past the nonspecific defenses

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Nonspecific Defenses

• This means that the identity of the
  pathogen/antigen is not important. The response
  is the same if a bacteria, virus, splinter or
  bullet invades the body.

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• Nonspecific Defenses
• First Line Defenses
• Skin Forms a physical barrier to pathogens
• -oils and sweat make skin acidic inhibits
  the growth of pathogens
• -lysozyme-enzyme found in sweat and tears
  digests bacterial cell walls
• Mucus Membranes-layers of tissue which secrete
  mucus
• - found in body openings and the respiratory
• system
• - mucus traps pathogens

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Nonspecific DefensesSecond Line Defenses

• Inflammatory Response
• Damaged cells release histamines chemical cry
  for help
• - histamines cause blood vessels to dilate
  (open) bringing
• blood to the area.
• - the dilated blood vessels become leaky
  releasing fluid and white blood cells in the
  infected area
• - causes swelling and redness in the damaged
  area
• - pus fluid and dead cells forms
• White Blood cells
• - Macrophages Big Eaters engulf and kill
  pathogens
• - Neutrophils-engulf bactera and release
  chemicals that kill the bacteria
  and themselves.
• - Natural Killer Cells recognize and kill
  virus infected
• 
  cells and tumors

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Textbook page 925

• Histamines are released Blood vessels
  dilate
• and
  leak

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Macrophage
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Nonspecific DefensesSecond Line Defenses
(continued)

• Temperature Response - Fever
• -Body temp increases in response to infection
• -pathogenic bacteria dont grow well at
  higher temp
• Proteins
• - Complement Proteins kill pathogens by
  punching a hole in the cell membrane
• - Intrerferon a protein released by cells
  infected by viruses
• -causes nearby cells to release an
  enzyme preventing the virus
• from reproducing

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Fevers help eliminate pathogens
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Specific Defenses

• Third Line of Defense
• Specific Defenses
• - identity of pathogen/
• antigen must be known
• - the specific immune
• response is tailored to
• the specific pathogen

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Specific DefensesMacrophage Links Nonspecific to
Specific

• When a macrophage engulfs a pathogen, it displays
  the viral antigen on its surface

The antigen is joined to a MHC (Major
Histocompatibility Complex) The MHC is a protein
on the surface of all vertebrate cells The
anitgen must be bound to the MHC for the Helper T
Cell to recognize it
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Specific DefensesHelper T Cells

• Receptor proteins on helper T cells (TH) bind to
  viral antigens displayed on the macrophage
• causes macrophage to release Interleukin1
• Interleukin1 activates
• the helper T cells (TH)

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Specific DefensesHelper T Cells continued

• Activated helper T cells (TH) release proteins
  called cytokines which activate cytotoxic T cells
  (TC) and B cells
• The activated (TC) and B cells begin to divide

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Specific Defenses Cell Mediated Response

• Receptor proteins on the
• cytotoxic T cells (TC) bind to
• viral antigens displayed by
• infected cells
• Cytotoxic T cells (TC) punch a
• hole in the cells membrane
• Your body produces many
• cytotoxic T cells (TC)
• - each specific to a particular antigen

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Specific DefensesAntibody Mediated Response

• B cells divide and develop into
• plasma cells
• Plasma cells release large numbers
• of antibodies
• Antibodies bind to antigens on
• pathogens
• Antibodies cause pathogens to clump
• holding them until macrophages
• can engulf them
• Antibodies are specific to a particular
  pathogen-your body produces the antibodies in
  response to infection

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The Specific Defense has two phases

• Primary Immune Response
• -Occurs when the body has never
  encountered a pathogen /antigen before.
• -Immune system goes through all of the steps
• -After the threat has passed, MEMORY Cells
  are made.

• Secondary Immune Response
• The next time the pathogeninvades MEMORY Cells
  identify the invader and a massive volume of
  antibodies are released, destroying the invader
  before you feel ill.
• You are immune!

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Vaccines
Polio 1952 60,000 cases in the US
3000 fatalities 1955 Salk vaccine 1979
eliminated in US
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How do vaccines work?

• Vaccines are made up of weakened viral particles.
• The weakened particles stimulate a small number
  of antibodies and memory cells to be produced.
  Primary Immune Response
• When a the pathogen attacks, the antibody
  production is larger.
• Secondary Immune Response

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Immune Response
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Vocabulary

• Pathogen B cells T cells
• Macrophages
• Nonspecific Defense
• Vaccines
• Primary Immune Response
• Secondary Immune Response