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