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The Immune Response. The Third Line of Defense. The third line of defense involves a specific response that is effective against specific pathogens. This involves a specialized group of white blood cells called lymphocytes, which produce antibodies.
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The Third Line of Defense • The third line of defense involves a specific response that is effective against specific pathogens. • This involves a specialized group of white blood cells called lymphocytes, which produce antibodies. • Antibodies are protein molecules that protect the body from invaders.
The Third Line of Defense (cont’d) • All cells have special markers located on their cell membranes, which are known as antigens (antibody generator). • Normally, the immune system does not react to the body’s own markers. • However, intruding cells or foreign proteins activate the production of antibodies.
The Third Line of Defense (cont’d) • There are two different types of lymphocytes found in the immune system. • The first is the T cell, which is produced in the bone marrow and is stored in a tiny organ called the thymus gland. • The T cell’s function is to seek out the intruder and signal the attack. • Acting much like a sentry, some T cells identify the invader by its antigen markers.
The Third Line of Defense (cont’d) • Once the antigen is identified, another T cell passes this information on to the antibody producing B cell. • B cells multiply and produce chemical weapons: the antibodies. • Each B cell produces a single type of antibody.
Antigen-Antibody Reactions • Antibodies are Y-shaped proteins that are produced to target specific foreign invaders. • Antibodies are specific; this means that an antibody produced against the influenza virus is not effective against HIV. • Each antibody has a shape that is complementary to its specific antigen.
Antigen-Antibody Reactions (cont’d) • There are many different antigen markers on the membrane of a virus or bacterium. • The attachment of antibodies to the antigens increases the size of the complex, making the antigen-antibody combination more conspicuous and, therefore, more easily engulfed and destroyed by macrophages.
Immune Response • Step 1: Pathogen enters body.
Immune Response (cont’d) • Step 2: Macrophages engulf pathogen and pushes the antigen markers to its outer membrane.
Immune Response (cont’d) • Step 3: A helper T-cell identifies the antigen present on the cell membrane of the macrophage.
Immune Response (cont’d) • Step 4: Helper T cells alert the B cells, which multiply and begin to produce antibodies.
Immune Response (cont’d) • Step 5: Antibodies attach to the antigens.
Immune Response (cont’d) • Step 6: Antibodies immobilize and tag invaders for macrophages to destroy.
Immune Response (cont’d) • Step 7: Helper T cells also send out chemicals to stimulate killer T cells. • Killer T cells puncture the cell membranes of intruders. If killer T cells find a viral coat attached to a cell membrane, the T cell attacks the infected cells.
Immune Response (cont’d) • Step 8: During the immune response, memory B cells and memory T cells are created. These cells contain a blueprint of the invader’s antigen. • This will allow the immune system to react faster the next time that particular antigen enters the body.
Immune Response (cont’d) • Step 9: A suppressor T cell ends the battle by signaling the immune system to return to its pre-infection state.
Immune Response • Step 1: Pathogen enters the body. • Step 2: Macrophages engulf pathogen and pushes the antigen markers to its outer membrane. • Step 3: A helper T-cell identifies the antigen present on the cell membrane of the macrophage. • Step 4: Helper T cells alert the B cells, which multiply and begin to produce antibodies. • Step 5: Antibodies attach to the antigens. • Step 6: Antibodies immobilize and tag invaders for macrophages to destroy. • Step 7: Helper T cells also send out chemicals to stimulate killer T cells. • Step 8: During the immune response, memory B cells and memory T cells are created. • Step 9: A suppressor T cell ends the battle by signaling the immune system to return to its pre-infection state.
