10.2 The Immune Response

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10.2 The Immune Response

• Some macrophages float throughout the bodyother
  stay in a fixed location
• The fixed macrophages are present in the spleen,
  lymph nodes and other lymphatic tissue

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Complement Proteins

• 20 known types
• Inactive under normal conditions
• Activated by marker proteins from invading
  microbes ? become messengers
• Immobilizes the invader
• A second group punctures the bacterial or fungal
  membrane
• A third group attaches to the invader

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Lymphocytes

• Specialized white blood cells that produce
  antibodies
• Antigens produces antibodies, present on the
  cell membranes and outer coats of viruses

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T Cells

• Produced in bone marrow and store in the thymus
  gland
• T cells seek out intruders and signal an attack
• Some T cells identify the invader by its antigen
  markers

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B Cells

• Multiply and produce antibodies
• Each B cell produces a single type of antibody,
  displayed on the cell membrane
• B cells are released from the bone marrow into
  the blood stream where some become plasma cells

Tutorial 18.4 Humoral Immune Response
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Antigen-Antibody Reactions

• Antibodies
• Y-shaped proteins engineered to target specific
  foreign invaders
• Similar tails, with variations at the outer edge
  of each arm

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Antigen-Antibody Reactions

• Different antigen markers are located on the
  membrane of a virus or bacterium
• As antibodies attach to antigen, the complex gets
  larger

Interaction of Antigen Presenting Cells and
T-helper Cells
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Receptor sites

• Found on different cellstoxins can affect
  different specific areas of the body
• The receptor site accepts a specific hormone or
  nutrient with a lock and key method
• Antibodies block toxins by binding the receptor
  sites

The Rockefeller University - The Body's Guard
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Viruses

• Also use receptor sites to enter cells
• DNA is injected into the cell, and the protein
  coat is left bound to its specific receptor
• Different viruses are specialized

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HIV

• Attaches to the receptor sites of the T cell
• The T cell engulfs the virus, but its protein
  coat is still attached to the receptor site
• The protein coat blocks the receptor site that
  normally binds invasive antigens
• Why is this a problem?

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Antibodies

• Antibodies bind to viruses, changing their shape
  so that the virus cannot bind the receptor sites
• A mutation will occasionally change the shape of
  the viral protein coat

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Recognition of Antigens

• Fig 7, pp. 469
• When a macrophage engulfs an invader, the antigen
  markers are pushed to its membrane
• Helper T cells read the antigens markers and
  release lymphokine
• Helper T cells later trigger B cells
• B cells form clones

Animation The Immune Response
Animations
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Killer T Cells

• Puncture cell membranes of intruders
• Kills body cells infected with viruses preventing
  the virus form reproducing
• Destroys mutated cellscancer?
• Organ transplant rejection?

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Suppresor T Cells

• Signal immune system to shut down
• Most B and T cells die off a few days after the
  infection is gone, but some remain for a long
  time after for protection
• Memory B cells

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Immune System Memory

• Immunity is based on maintaining an adequate
  number of anitbodies
• Memory B Cell
• Generated during an infection, holds a blueprint
  of the antigen or antigens that characterize the
  invader

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Matching Tissues for Organ Transplant

• The donor organ is usually identified as an
  invader by the protein markers on its cell
  membrane
• The recipient makes antibodies to destroy the
  foreign invader

Humoral Immunity Introduction