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Question 1

Skin and mucous membranes help exclude ___ from the body.

Answer 1

pathogens

Any pathogens that do enter may be attacked by white blood cells, such as macrophages and neutrophils.

Question 2

Pathogens may also stimulate

Answer 2

an inflamma­tory response or an increase in body temperature.

Question 3

The immune system consists of an army of various kinds of

Answer 3

white blood cells: macrophages, killer T cells, helper T cells, and B cells.

Question 4

Helper T cells stimulate ___. Helper T cells also ___

Answer 4

killer T cells, which attack pathogens and infected cells.

stimulate B cells, which release antibodies that mark pathogens for destruction.

Question 5

In autoimmune diseases, the body fails to

Answer 5

distinguish its own cells from those of a pathogen and thus attacks its own cells.

Question 6

In allergies, the body responds to a

Answer 6

harmless substance such as pollen or dust as if it were a pathogen.

Question 7

AIDS is caused by the

Answer 7

human immunodefi­ciency virus (HIV), which destroys helper T cells in large numbers, thereby disabling the immune system.

Question 8

3 lines of defense:

Answer 8

1st line: Skin main protection is barrier.

2nd line: Counterattacks (non-specific)

3rd line: The Immune System

Question 9

1st line of defense:

Answer 9

Skin main protection is barrier. Constantly replaced cells. Secondary defense on skin is oil and sweat that makes make surface acidic and have lysozyme enzyme that can break down some bacterial cell walls.

Internal surfaces (digestive tract, respiratory tract and reproductive tract) protected by mucous membranes - secrets mucus which traps pathogens and invaders. Cilia continually sweep mucus upward to be swallowed and then killed by stomach acid.

Question 10

2nd line of defense:

Answer 10

Counterattacks (non-specific)

1. CELLULAR DEFENSE - Cells that kill microbes:

Macrophages - white blood cells kill bacteria one at a time by ingesting.
Neutrophils – white blood cells cell invaders and selves by secreting chemicals identical to household bleach.
Natural killer cells kill infected cells by puncturing cell wall so water can swell and burst it. Very good at detecting and attacking virus infected cells, thus preventing them from making more viruses. NOTE: They are also the body’s best defense against cancer.
2. PROTEIN DEFENSE (compliment)- chemicals that circulate in blood until they find bacteria and fungi, then the interact to form MAC (membrane attack complex) which is inserted into invader cell walls and creates a hole.

3. INFLAMMATORY RESPONSE – injured or infected cells send alarm that cause dilation of local blood vessels - to increase blood flow (AND defenders) to region. Promote migration of macrophages and neutrophils (arrive first) to site. Dilation of capillaries causes their walls to be thinner and leakier to allow cellular defense easier access to infection site. Symptoms: redness, swelling.
4. TEMPERATURE RESPONSE – general rise in body temperature, making body inhospitable for pathogenic reproduction.

Question 11

3rd line of defense

Answer 11

The Immune System

White blood cells which are produced in bone marrow circulate in blood and lymph. 2% of body cells.

The 3rd line is called the “specific” defense because it only fights a specific pathogen - marker by a specific marker protein/antigen.

The 3rd line is called the “immune” defense because after the battle has been won some B cells become memory B cells and if they ever see the specific marker protein/antigen again they will call up the 3rd line of defense even before the 2nd line is engaged in the battle.

Question 12

3 kinds of Immune System white blood cells:

Answer 12

Killer T cells
B cells
Helper T cells

Question 13

Killer T cells

Answer 13

attack and kill infected cells by puncturing a hole

Question 14

B cells

Answer 14

produce and release antibodies, which label pathogens and infected cells for destruction by macrophages, neutrophils, killer T and Natural Killer cells

Question 15

Helper T cells

Answer 15

activate Killer T and B cells.

Question 16

Immune system response sequence:

Answer 16

1. Macrophages fighting in the 2nd line of defense, sensing the battle is being lost, release protein alarm signal Interleukin-1 which activate specific Helper T cells. There are millions of different kinds of Helper T cells BUT only the few that have receptor proteins that most closely match the marker proteins of the pathogen (antigens) that are displayed on the alerting macrophage, are the ones that respond. Note: when macrophages ingest a pathogen they display some of the pathogen’s marker proteins (the antigen) on their surface
2. These specific Helper T cells release Interleukin-2 which activates specific Killer Ts and specific Bs. There are millions of different kinds of Killer T and B cells BUT only the few that have receptor proteins that most closely match the marker proteins of the pathogen (antigens) are the ones that respond to the specific Helper T cell.
3. Killer T side - Because every person has only a few specific Killer T cells (at first) that can respond to a particular pathogen, the first thing they do is divide rapidly to increase their numbers. Then these specific Killer Ts attack and puncture infected cells identified by viral protein markers on its surface.
4. B cell side - Because every person has only a few specific B cells (at first) that can respond to a particular pathogen, the first thing they do is divide rapidly to increase their numbers. Then Bs produce and release specific protein antibodies that match the antigen/marker protein of the pathogen. These antibodies are released into blood stream and attached to the antigens on pathogens or pathogen antigens displayed on the outside of infected cells. The antibodies mark these targets for destruction by macrophages, neutrophils, killer T and Natural Killer cells. B cells divide rapidly to create more cells to produce mass quantities of antibodies. B cell defense is the most powerful side of the 3rd line of defense because it amplifies reaction to a specific pathogen a millionfold.
5. Immunity - After the initial infection battle is won…..some B cells become memory cells that remain in the body for a long time. If the pathogen ever shows up again, the Memory B cells will recognize and “remember” the pathogen’s marker protein (antigen) and activate the 3rd line of defense (the second line of defense does not have to be engaged and losing the battle). The 3rd line is immediately called up to quickly eliminate the threat before you even feel sick.

Question 17

Two ways of acquiring immunity:

Answer 17

-Being exposed to the pathogen’s marker protein by Getting Sick
-Vaccination
For some pathogenic illnesses we cannot develop of long-term immunity because the genes for the pathogen’s marker proteins mutate often.

Question 18

Vaccination

Answer 18

process of introducing killed or weakened pathogen, or harmless microbe with surface protein of pathogen, into body to stimulate an immune reaction and production of memory B cells, to protect against future invasion.
(Does not work with viruses that have rapidly evolving surface proteins because the memory cells will not recognize the new marker proteins.)

Question 19

Many bacteria can develop resistant to our antibiotics because we do something inappropriately like:

Answer 19

• Not taking the antibiotic for the prescribed time. If we stop after we feel better and do not finish the regimen, the only bacteria that will have been killed off are the less-resistant. The more resistant will survive to reproduce.
• We take an antibiotic for an pathogen that it will not work on (like a virus). Any bacteria that may be in our body towards the end of the regimen will be exposed to the antibiotic (selective pressure) but not long enough to kill off the more resistant.
• Putting antibiotics in livestock feed. Any bacteria that may be in our body when we eat that meat will be exposed to the antibiotic (selective pressure) but not long enough to kill off the more resistant.

Question 20

Autoimmune diseases

Answer 20

body fails to recognize own cells and attacks own tissue. Multiple Sclerosis – disease strikes 20-40 year olds, causes the destruction of myelin sheath of nerve cells eventually disabling nerve transmission (both voluntary and involuntary muscles rely of nerve impulses). Autoimmune disease result when helper T and Killer T cells that may have receptor proteins that match your own…. go to the Thymus where they should be killed….but they are not killed and they end up being released and targeting cells of your own body.

Question 21

Allergic reaction

Answer 21

body responds to harmless substance as though it was a pathogen.

Question 22

HIV transmitted by

Answer 22

exchanging of body fluids (semen or vaginal secretions) during unprotected sex or mixing of contaminated blood by sharing needles. The reason why these fluids pose a danger of infection is that they have many macrophages that have many viral particles inside.

Question 23

HIV infection sequence:

Answer 23

• HIV has a marker protein that triggers/tricks -macrophages to engulf it.
• Because HIV is a retrovirus, reverse transcriptase (an enzyme it carries) first has to transcribe viral RNA into DNA, so it can then make the macrophages make more copies.
• When more copies are made, they leave the macrophages gently without killing the macrophages. This is problematic because the macrophages are still alive and able to do their defensive jobs, so the person will not get sick BUT is totally contagious and can spread the virus without knowing it.
• At sometime later (we don’t know why or when) the virus changes a marker protein, which now allows it to trick Helper T cells to take it in.
• When the virus is replicated by Helper Ts, so many are made so fast that they burst out of the helper T cell and kill it. This is problematic because without sufficient Helper Ts the body cannot call up the 3rd line of defense to respond to pathogens and cancers. The patient eventually succumbs to infections by pathogens or cancer that would normally be rendered harmless by a healthy system.