Download Immune system summary

1. 40–2 The Immune System
The function of the immune system is to fight infection through
the production of cells that are able to identify and destroy foreign cells
and materials that do not belong in the body. This system relies on a
series of different cells that can recognize, attack, destroy, and
“remember” each type of pathogen, something that can make you sick,
that enters the body. This process is called immunity.
The immune system has nonspecific defenses to stop pathogens from
entering the body or attacks all pathogens the same way. These
defenses include physical and chemical barriers.
• First line of defense. The function of the first line of defense is to keep
pathogens out of the body. This role is carried out by skin, mucus, sweat,
and tears. Your body’s most important nonspecific defense is the skin. It
forms a barrier that few pathogens can get through. Mucus, saliva, and
tears trap pathogens and contain an enzyme that kills bacteria.
• Second line of defense. When pathogens do enter the body, other
nonspecific defenses go to work. The inflammatory response is a
nonspecific defense reaction to tissue damage caused by injury or
infection. Blood vessels near the wound expand. Specialized white blood
cells called macrophages, enter the tissues to fight infection.
Macrophages look for and identify foreign materials based on unique
proteins and carbohydrates these materials carry. The unique proteins
and carbohydrates a cell or virus has is called antigens when the immune
system starts to attack them. After the macrophage attacks and destroys
the foreign cell,the macrophage takes the antigen to the B cells and T
cells to begin the specific part of the immune response. A fever, or higher
than normal body temperature, can slow pathogen growth. A fever serves
to slow the reproduction of the pathogen (usually a virus or bacteria) so
the immune system has a better chance of removing them.
If a pathogen gets past the nonspecific defenses or continues to grow in
number, specific immune defenses go to work. This is called the immune
response. There are two types of immune response.
• In humoral immunity, white blood cells, called B cells, make unique
proteins called antibodies that attack the pathogen in the blood. Antibodies
are proteins that recognize and bind to the antigens found on the surface
of the pathogens. Each B Cell is only able to produce one type of antibody.
Different antibodies must be made for each different pathogen that enters
the body
• In cell-mediated immunity, white blood cells, called helper T cells, find
and destroy abnormal or infected cells. Helper T cells are specific to the
pathogen they can recognize. Each helper T cell can only recognize one
antigen or pathogen. When the correct helper T cell is found, the helper T
cells activates cytotoxic (killer) T Cells. Cytotoxic T Cells multiply and
travel in the blood stream looking for any cells with the antigen. When the
antigen is found, the cell is destroyed. After a pathogen is destroyed,
memory cells are formed. These cells respond if the same pathogen
enters the body again. Both B cells and T cell form memory cells so that
the body can fight off the pathogen more quickly in the future. Having
memory cells give an individual immunity to the disease.
You can acquire immunity without having a disease. Vaccination is the
injection of a weakened or mild form of a pathogen to cause immunity.
Immunity that results from vaccines is called active immunity. Active
immunity appears after exposure to an antigen. Passive immunity forms
when antibodies are introduced into the body. Passive immunity lasts only
as long as the antibodies stay in the body.
Besides vaccinations, bacterial infections can be treated with antibiotics,
medications that only harm bacterial cells by destroying their cell walls.
Unfortunately, antibiotics have been misused and many types of bacteria
have evolved immunity to these antibiotics.
Immunodeficiency diseases occur when the immune response
breaks down. AIDS is one example of an immunodeficiency
disease. AIDS is caused by HIV (human immunodeficiency virus).
HIV attaches to receptors on helper T cells. Once inside the cells,
HIV copies itself and kills the infected helper T cells. HIV gradually kills off
all the helper T cells. As a result, the immune system can no longer fight
infections. AIDS can be transmitted from mother to child during pregnancy,
childbirth, and breast-feeding. It can also be transmitted from one person
to another through shared needles, contact with infected blood, and sexual
intercourse. The only no-risk behavior with respect to HIV and AIDS is
abstinence.
Questions:
1. What is the purpose of the immune system?
2. What can pathogens do to the body?
3. What is the first line of defense for the immune system?
4. When does the second line of defense start?
5. What is the inflammatory response?
6. What is a macrophage?
7. What is an antigen?
8. What does the macrophage do with the antigen?
9. What is the purpose of a fever?
10. Describe humoral immunity?
11. What is an antibody?
12. Describe cell mediated immunity?
13. What is the difference between a helper T cell and a cytotoxic T cell?
14. What are memory cells?
15. How do memory cells give an individual immunity?
16. How does a vaccination help a person?
17. What do antibiotics do?
18. What virus causes AIDS?
19. What does HIV do to the body?
20. How doe HIV spread?
For the following statements, match the correct term. Terms may be
used more than once, some answers may have more than one
answer.
Helper T-Cell
B-cell
Macrophage
Skin
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Divides and activate the cytotoxic Cells
Produces antibodies
Prevents pathogens from entering the body
Activates with specific antigens
Tries to stop all pathogens equally
Can become a memory cell
Produces proteins that attach to antigens
Use the graph to answer the following two questions.
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Determine if the following statements are true or false. If false, rewrite
the statement to make it correct.
An antibody is a protein or carbohydrate an immune cell cannot
recognize.
Helper T Cells help to activate both B cells and cytotoxic T cells.
The skin and B cells are a part of the nonspecific defense.
A vaccination can help to produce memory cells.
The HIV virus attacks the macrophages of the immune system.
An antibody is able to attach to many different antigens.
A person can only get immunity to a pathogen by getting sick.
Cytotoxic T cells make antibodies.
Inflammation causes more macrophages to arrive at a possible
infection.