10.2 The Immune Response
• Some macrophages float throughout the body…other stay in a fixed location
• The fixed macrophages are present in the spleen, lymph nodes and other lymphatic tissue
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
Lymphocytes
• Specialized white blood cells that produce antibodies
• Antigens: produces antibodies, present on the cell membranes and outer coats of viruses
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 it’s antigen markers
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
Antigen-Antibody Reactions
Antibodies:
• Y-shaped proteins engineered to target specific foreign invaders
• Similar tails, with variations at the outer edge of each arm
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
Receptor sites
• Found on different cells…toxins 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
Viruses
• Also use receptor sites to enter cells
• DNA is injected into the cell, and the protein coat is left bound to it’s specific receptor
• Different viruses are specialized
HIV• Attaches to the receptor sites of the T cell
• The T cell engulfs the virus, but it’s 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?
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
Recognition of Antigens
• Fig 7, pp. 469• When a macrophage
engulfs an invader, the antigen markers are pushed to it’s membrane
• Helper T cells read the antigen’s markers and release lymphokine
• Helper T cells later trigger B cells
• B cells form clones
Animations
Animation: The Immune Response
Killer T Cells
• Puncture cell membranes of intruders
• Kills body cells infected with viruses preventing the virus form reproducing
• Destroys mutated cells…cancer?
• Organ transplant rejection?
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
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
Matching Tissues for Organ Transplant
• The donor organ is usually identified as an invader by the protein markers on it’s cell membrane
• The recipient makes antibodies to destroy the foreign invader
Humoral Immunity: Introduction