Transcript The Immune System

The Immune System
I. Agents of Disease
1. Viruses (influenza, small pox)
2.Bacteria ( botulism, diphtheria)
3.Protists ( malaria, sleeping sickness, amoebic dysentery)
4. Worms(schistosomiasis)
5.Fungi( ringworm)
II. How diseases are spread
1.Physical contact
2. Contaminated food and
water
3. Infected animals (vectors)
III Fighting Infectious
Diseases
1.Antibiotics
2.Antiviral Drugs
3.Over –the-- Counter Drugs
Immune system
-functions to fight infection through the production of
cells that inactivate foreign substances or cells
-2 general categories of defense mechanisms:
I. Nonspecific Defenses
 Do not discriminate between 1 threat and another; include physical and
chemical barriers
A. First line of Defense
1. Function: to keep pathogens out of the body
2. Carried out by skin, mucus, sweat and tears
3. Body’s most important nonspecific defense is the skin.
Lysozyme– an enzyme that breaks down the cell walls of many bacteria.
Second line of Defense
1. Inflammatory response- a second line of defense
2. when pathogens are detected immune system produces
millions of white blood cells(WBCs), which fight infection
3. Blood vessels near the wound expand and WBCs move from
the vessels to enter the infected tissues.
4. Many of these WBCs are phagocytes, which engulf and
destroy bacteria.
5. Infected tissues become swollen and painful.
6. Immune system releases chemicals that increase the core
body temperature(FEVER)
Interferons
1. Produced by virus-infected cells
2. Are proteins that help other
cells resist viral infections
3. Inhibit the synthesis of viral
proteins
4. Help block viral replication
5. Slows down the process of
infection and gives the specific
defenses of the immune system
time to respond.
Specific Defenses(immune response)
Antigen- any substance that enters the body
to rigger the immune response.
Humoral Immunity
Provides immunity against antigens and
pathogens in the body fluids
Fighting cells in this response: B
lymphocytes( B cells)
B cells sense pathogens, grow and divide
rapidly, producing large #s of plasma cells
and memory B cells
Plasma cells release antibodies, proteins
that recognize and bind to antigens
Antibodies carried in the bloodstream to
attack pathogens
Once body is exposed to a pathogens,
millions of memory B cells remember how
to produce antibodies specific to that
pathogen– secondary response (reduce
chance that the disease can develop a 2nd
time.)
Cell-Mediated Immunity
Defense against its own cells and pathogens inside
living cells
2. Fighting cells in this response: T cells
3. The body’s primary defense against it own cells when
they have become cancerous or infected by viruses.
4. Also important infection caused by fungi and protists
5. When viruses get inside living cells, antibodies alone
unable to destroy them.
6. T cells divide and differentiate into:
a. Killer T cells(cytotoxic T cells)/these track down and
destroy bacteria, fungi, protozoan or foreign tissue that
contains the antigen
b. Helper T cells—produce memory T cells
c. The memory T cells—cause a secondary response if
the same antigen enters the body again
d. Suppressor T cells—release substances that shut
down killer T cells after the pathogenic cells brought
under control.
1.
Antibody Structure
•Shaped like the letter Y
•Has 2 identical antigen-binding sites
•Small differences in the amino acids affect
the shaped of the binding sites; make
antibody the ability to recognize to an
antigen with a complementary shape
Transplants
Transplant
• T cells make acceptance of organ transplants difficult.
• Rejection- immune system damages and destroys the
transplanted organ
• Donors sought whose cell markers nearly identical to cell
markers of recipient
• Recipients take drugs to suppress the cell-mediated
immune response
Acquired Immunity
Active Immunity
1. Vaccination- the injection of weakened or mild form of pathogen to produce
immunity.
2. Edward Jenner credited w/1st vaccination for smallpox
3. Vaccines stimulate the immunity system to produce millions of plasma cells ready to
produce specific types of antibodies
4. More than 20 serious human diseases have vaccine
5. Occurs after exposure to an antigen
6. May result from natural exposure to an antigen or from deliberate exposure to the
antigen.
Passive Immunity
1.
2.
3.
Produced when antibodies from other animals against a pathogen are
injected into bloodstream.
Lasts only a short time b/c the body eventually destroys the foreign
antibodies
Can develop naturally or by deliberate exposure
Ex: passing of antibodies from mother to fetus in development or in early
infancy via breast milk protects a child from many infectious diseases for
many months
Immune System Disorders
I.
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Allergies
overreactions of the immune
system to antigen.
Common allergens: pollen,
dust,mold & bee stings.
Mast cells-specialized immune
system cells that initiate the
inflammatory response and
release histamines.
Histamines- chemicals released
by activated mast cells
- increase flow of blood and
fluids to surrounding area and
increase mucus production.
Antihistamines- drugs that are
used to counteract the effects of
histamines.
II. Asthma
 a chronic respiratory disease in which the air passages become
narrower than normal.
 Heredity and environmental factors ( pollution, smoke)
 a leading cause of serious illness among children (life- threatening)
 An asthmatic attack triggered by emotional stress, pollen, cold air,
certain medication, respiratory infection, tobacco smoke etc.
 No cure, but some medications relax the smooth muscles around the
airways, making breathing easier.
Autoimmune Diseases
 Cause- when the immune system
makes a mistake and attacks the body’s
own cells.
 “anti-self” antibodies
 Ex: Type I Diabetes, rheumatoid
arthritis, myasthenia gravis and multiple
sclerosis(MS)
 Some are treated with medication that
alleviate symptoms.
Ex: insulin injection- Type I Diabetes
and some medications that suppress the
immune response
AIDS ( Acquired Immune Deficiency Syndrome)
 2 types- immune system fails to develop
normally and AIDS-results from a viral infection
that destroy helper T cells.
 HIV-retrovirus that causes AIDS.
 HIV attacks Key T cells in the immune system,
destroying the body’s defense.
 when HIV virus attacks a helper T cell, it
attaches on the cell membrane- once inside, the
virus forces the host cell to make DNA copies of its
RNA, then the new virus leaves the T cell and
destroys more.
 HIV can be transmitted by
(Sexual intercourse, shared needle, contact with
blood/products and from mother to child during
pregnancy, nursing.)with an infected person
 the only prevention is ABSTINENCE
No cure, but currently multidrug and
multivitamin "cocktails” can fight the virus.