the immune system life science 2010 鄭先祐 (ayo) 製作

The Immune System

Life Science 2010

鄭鄭鄭 (Ayo) 製作

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The immune system

There are two basic lines of defense.– the nonspecific responses – the specific responses.

Table 20.1 The nonspecific responses Barriers of the body covering inflammatory response

– clotting mechanisms – phagocytes engulf invaders.

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Essay 20.1 Lyme disease

It is a disease caused by a spirochete, a bacterium, Borrelia burgdorferi, and carried by a tick.

The tick has three stages in its life cycle. In its larval stage, it mainly infects the white-foote

d mouse. In its nymph stage, it infects a range of mammals,

including dogs, raccoons, and humans. In its adult stage, it mainly infects white-tailed dee

r.

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Lyme disease

The disease was first identified in 1975 in Lyme, Connecticut, and has since spread swiftly throughout the United States.

There may have been 50,000 cases in 1989 alone.

The first sign of the disease may be flu-like symptoms, including headache, fever, weakness, and stiff joints.

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Lyme disease

If antibiotics, such as tetracycline or doxycycline are administered immediately, the victim is likely to recover.

As time passes without diagnosis and proper treatment, a debilitating arthritis( 關節炎 ) may appear from which the victim may never recover.

The bacterium may invade the brain and spinal cord, producing dizziness( 昏眩 ), incoherency, visual problems, and numbness ( 痲痺 ).

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The nonspecific responses

Once any organism invades, it triggers an inflammatory response ( 紅腫反應 ).

It begins as the cells begin to secrete histamine, which dilates tiny arterioles bringing more blood to the injured area.

Fever is triggered either by toxins produced by the invading organism or by pyrogens, chemicals released by certain white blood cells as they respond to an invasion.

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Fig. 20.1 Nonspecific responses

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Fig. 20.2 There are five major types of leukocytes.

中性球單核球嗜鹼球

嗜酸球淋巴球

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五種白血球的功能 Phagocytes 的有三種： eosinophils, neutro

phils, 和 monocytes.– Eosinophils primary response to allergies and p

arasitic infections.– Neutrophils are frontline soldiers.They produce

toxic substances against invaders.– Monocytes arrive next, in great numbers, and o

nce they encounter the invader they begin to undergo remarkable changes, growing and swelling until they become huge macrophages.

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Fig. 20.3 A macrophage capturing bacteria.


五種白血球的功能 Lymphocytes produce both cells and

proteins that interact in both nonspecific and specific responses.– The natural killer cell(NK cell) is active in the

nonspecific response. They roam the body.– When they encounter cancerous cells or cells

harboring viruses, they immediately attack those cells.

Basophils secrete histamine that intensifies the inflammatory response.


淋巴球的類別與功能 (cf. Table 20.2)

Cytotoxic T-cell ： destroys virus-infected and cancerous cells.

Helper T-cell ： stimulates B-cell and cytotoxic T-cell proliferation.

Suppressor T-cell ： slows down immune response.

B-cell ： secretes antibodies Natural killer cell ： directly destroys

virus-infected cells and cancerous cells.


Essay 20.2 allergy ( 過敏反應 ) The pollen attaches to specific

antibodies on large, granule-containing "mast cells" that line the respiratory passages.

The granules are then explosively released, triggering the production of histamine and other chemicals that cause inflammation.


Allergic reactions can also produce a dangerous condition called anaphylactic shock.

This happens when large areas of the body produce an allergic reaction, as when an individual allergic to bee stings or penicillin receives those antigens and they are rapidly transported throughout the body.

In such a case, capillaries throughout the body become leaky and blood pressure sudden drops, reducing blood flow to the brain and heart.

Death can result unless epinephrine (adrenaline) is quickly administered.


A historical case In the fourteen century, European cities wer

e crowded, dirty, and filled with travelers. Conditions were right for a flea( 跳蚤 )-bor

ne pathogen, Pasteurella, to sweep repeatedly through the population causing bubonic plague, or Black Death ( 黑死病 ).

Within a few years, one-quarter of the population of Europe had been killed.


Specific responses

Two kinds of lymphocytes play a critical role in the specific responses.– These are the B-cells and the T-cells.

B-cells are specialized to do two things– plasma cells make antibodies to combat the inv

ader. (humoral immunity)– memory B-cells 記憶過去曾經產生過的抗體

資料。


cellular immunity T-cells are involved in cellular immunity. There are three basic kinds of T-cells.

– Helper T-cells ( 幫助者 ), interact with other cells to enhance the immune response.

– cytotoxic T-cells ( 殺手 ), identify infected cells and rupture their membranes

– suppressor T-cells ( 壓抑 ), help call off the body's defenses.


抗原 - 抗體反應 Antigens are foreign

molecules that elicit an immune response in the host organism.

Antibodies are proteins produced by the host plasma cells that identify and help destroy antigens, including the cells that bear antigens.

Fig. 20.4


When a specific antigen is encountered, the recognition regions of the antibody molecules attach to specific binding sites on the antigen that can be engulfed by a macrophage.

Fig. 20.5

巨喫細胞


Fig. 20.6 In the ongoing combat against invaders.

巨喫細胞吞食抗原，再將抗原送至膜外。

Helper T-cell 受到激發，分泌 interleukin 。

Interleukin 刺激 cytotoxic T-cells 和 memory cells 的 production.


Fig. 20.7 B-cells begin their own

arousal by capturing antigen and preparing a recognition site that will match that of a chosen helper T-cell.

When they bind together, interleukin secreted by the helper T-cell activated the B-cell and plasma, and memory cells are produced.


Primary and secondary response

Those defenses can be divided into two stages: the primary response and secondary response.

Primary response occurs when a foreign substance is encountered for the first time.

The secondary response is the sequence that is triggered by the army of memory cells produced by the primary response.


Self-tolerance and autoimmunity

All the cells of the body bear their own molecular "markers" embedded in their membranes.

所有的免疫細胞巡邏全身，只要有這些 markers 的細胞，就不會攻擊。

This acceptance by the body's immune cells is called-tolerance.

In some case, the immune system can turn against its own body, the reaction is called autoimmunity.


Interferon ( 干擾素 )

Interferon causes cells to become resistant to attacks by other viruses.

It does not act against specific viruses but will inhibit any viral attack.

Given interferon in a nasal spray 可以避免感冒。 Interferon reduced brain tumor size. Side effects: it triggers irregular heartbeats, it may

also complicate liver or kidney problems.


Essay 20.3 How African crocodiles defend against Texan rabbits

If you take hemoglobin from a rabbit and inject it into a crocodile, the crocodile will form antibodies against the rabbit hemoglobin.

Why can this be? There are only about 300 DNA

segments that code for the variable DNA segments of antibodies.


Recombination of DNA

Only 300 DNA segments clearly not enough to provide an antibody response against every possible antigen.

However, these regions are extremely unstable. They break apart and rejoin endlessly, providing a virtually infinite number of combinations (in humans, about 180 億 ).


AIDS AIDS ： acquired immuno-deficiency synd

rome ( 後天免疫失調症候群 ) The first case of AIDS in the United States

appeared in 1979, followed by a half-dozen cases reported in Los Angeles in 1981.

In early 1989, the world Health Organization estimated that over one new case of AIDS was developing each minute, worldwide.


In 1995, it was reported between 63 萬 and 89 萬 7千人感染 AIDS 。

It is estimated that between 6 and 10 million people are presently affected with the virus but do not yet show symptoms.

Many people carry antibodies to the virus that causes AIDS, showing that they have been exposed to it, without developing the symptoms.

The syndrome, once full blown, is incurable and virtually always cause death within a few years (fewer than 14% of victims survive past three years).


Fig. 20.8 AIDS manifests itself in numerous ways, all marked by a deteriorating immune system.

Early signs of AIDS include a series of lingering( 慢性的 ), simple colds, night sweats, persistent fever, swollen glands, and coughing.

More serious conditions follow, including at least three forms of cancer and destruction of the lungs and brain (Fig. 20.8)


Fig.20.9 AIDS is especially prevalent among needle-sharing addicts.


Dependence on condoms as a protection

Some types of condoms are not completely effective.

For example, those made of animal membranes, rather than rubber, do not block the passage of viruses.

Also some men simply do not know how to use them safely.(The condom-sheathed penis must be withdrawn immediately after ejaculation).


The geographical source of HIV

HIV(human immunodeficiency virus) 原本是在 African green monkey (West Afr

ica) 身體內的 virus 轉入人體。從西非傳至海地，美國同性戀者渡假地

區。再經由這些同性戀者，傳入美國。然後，逐漸擴展至全球。無論是同性或異性戀，都可以傳染。


Essay 20.4AIDS The infectious a

gent of AIDS was discovered in 1984.

The virus is called HIV (human immuno-deficiency virus).


HIV 攻擊 T- 細胞的過程。


HIV 攻擊 T- 細胞的過程。 The virus attacks the helper T-cell, penetrating

the the cell and releasing a single strand of RNA and an enzyme, reverse transcriptase, with it.

The enzyme enables the RNA to make a double strand of complementary DNA, which then joins the helper T-cell's DNA.

Finally, there are so few helper T-cells in the blood that no effective immune response can be mounted against any attack whatsoever.


AIDS virus seeks out the helper T-cell lymphocytes. Using the various chemical markers on its surface, the

AIDS virus binds easily to a receptor on the surface of the helper T-cell.


The HIV injects RNA and the enzyme transcriptase into T-cell. The enzyme helps transcribe the invading RNA into DNA. Once activated, the viral DNA directs the T-cell to make copies of the

virus. Eventually the host cell dies.


Mind and Body People have long noticed a relationship

between mood and illness. Depressed people seem to get sick more

often than happy, cheerful people. The link between the mind and the immune

system has even been shown in other species.

But how could mind influence immunity? The answer isn't clear yet.


Mind and Body Scientists have discovered that neuropeptid

es, once believed to be restricted to the brain, are found throughout the body.

They are chemically related to substances that help regulate the immune system.

Some researchers suggest that neuropeptides are the link between the immune system and the brain.


Essay 20.5 The mind-immunity link

The controversy began in the 1980s when a purported link between depression and lowered immunity was described.

Correlations were made between the proliferation of white blood cells, as well as other aspects of the immune response, and depressed individuals, such as those who were told they were HIV positive, those caring for spouses with Alzheimer's disease, those who had lost a mate, or even those who had moved.

However, the results were not clear-cut.


The mind-immunity link Younger depressed patients retained normal immune

response, while older one saw declines in their number of helper T-cells and natural killer cells.

Some studies have shown that stress can reactivate herpes viruses and promote the appearance of cold sores, genital herpes, and mononucleosis.

The stress in these cases ranged from taking exams, to becoming divorced, and to caring for the ill.


The mind-immunity link

People under high stress often fall victim to behaviors that lower their resistance to infection, such as alcohol abuse, smoking and sleeplessness.

There are those, by the way, who object to the idea that people can be responsible for their own illness.

However, the jury is still out on the relationship of mental attitude and good health.


Most of us wish to live long and well. But that implies a continuing existence on an essentially hostile planet.

Furthermore, that hostility may be increasing, largely because of our own behavior.

We must rely on new technologies to help us solve our immediate problems, and the Earth is becoming permeated with technology's by-products. Many Chemicals are totally new to environment.

Indeed, our immune systems, and our ability to withstand, may soon be tested in ways we can only imagine.


An ethical concern

Interleukin-12 (IL-12)is produced normally by the immune system but can be produced at great expense by pharmacologists.

When administered to a patient, it "jump starts" cell-mediated immunity and is effective against viruses, bacteria, fungi, protozoa, worms, and possibly AIDS.

Drug companies are hesitant to produce IL-12, because there will be little profit from the Third World countries with little money.


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the immune system life science 2010 鄭先祐 (ayo) 製作

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