Transcript le ch. 23 immunity_from_disease

Chapter 23 Immune System
What You’ll Learn
You will describe how infections are transmitted
and what causes the symptoms of diseases.
You will explain the various types of innate and
acquired immune responses.
• You will compare antibody and cellular
immunity
23.1 Infectious diseases
• Section Objectives:
• Describe how pathogens are transmitted.
• Explain what causes the symptoms of a disease.
What is an infectious disease?
• Disease-producing agents
such as bacteria,
protozoans, fungi, viruses,
and other parasites are
called pathogens. (NOT all
microorganisms are
pathogens
• main sources of pathogens
are soil, contaminated
water, and infected animals,
including other people.
Reservoirs of pathogens
Transmission of disease
• Pathogens can be transmitted to a host from
reservoirs in four main ways: by direct contact, by an
object, through the air, or by an intermediate
organism called a vector.
Transmission of disease II
• The common cold,
influenza, and STDs are
spread by direct
contact.
Transmission of disease III
• Bacteria and other
microorganisms can be
present on nonliving objects
such as money, toys, or
towels.
• Transmission occurs when
people unknowingly handle
contaminated objects.
Transmission of disease IV
• Airborne transmission of a disease can occur when a
person coughs or sneezes, spreading pathogens
contained in droplets of mucus into the air.
Transmission of disease V
• Diseases transmitted by
vectors are most commonly
spread by insects and
arthropods
• malaria and the West Nile
virus are transmitted by
mosquitoes.
• Lyme disease and Rocky
Mountain spotted fever are
diseases that are
transmitted by ticks.
• Flies also are significant
vectors of disease.
What causes the symptoms of a disease?
• When a pathogen invades your body, it encounters
your immune system.
• If the pathogen overcomes the defenses of your
immune system, it can metabolize and multiply,
causing damage to the tissues it has invaded, and
even killing host cells
Damage to the host by viruses and
bacteria
• Most of the damage done to host cells by bacteria is
inflicted by toxins.
• These poisons can inhibit protein synthesis in the
host cell, destroy blood cells and blood vessels,
produce fever, or cause spasms by disrupting the
nervous system.
Patterns of Diseases
• Some diseases, such as typhoid fever, occur only
occasionally in the United States.
• On the other hand, many diseases are constantly
present in the population-endemic disease. Ex.
Common cold
Treating Diseases
• 1 way: An antibiotic is a substance produced by a
microorganism that, in small amounts, will kill or
inhibit the growth and reproduction of bacteria.
• Your body also has its own built-in defense system—
the immune system —that works to keep you
healthy.
23.2 The Immune System
• Section Objectives:
• Identify the cells, tissues, and organs
make up the immune system.
that
• Compare innate( nonspecific) and acquired
(specific)immune responses.
• Distinguish between antibody and
immunity.
cellular
• Summarize the structure of the lymphatic system
• Distiguish between passive and active immunity
Lines of defense
• 1st line: Barriers
– broad, external defense
• “walls & moats”
– skin & mucus membranes
• 2nd line: Non-specific patrol
– broad, internal defense
• “patrolling soldiers”
– phagocyte (eating) WBCs
• 3rd line: Immune system
– specific, acquired immunity
• “elite trained units”
– lymphocyte WBCs & antibodies
• B & T cells
Innate Immunity
• The body’s earliest lines of defense
against any and all pathogens make up
your nonspecific, innate immunity.
Nonspecific defense I
• 1st line of defense:
• Skin Intact skin is a
formidable physical barrier
to the entrance of
microorganisms
• Body secretions
mucus traps many
microorganisms
• Sweat, tears, and saliva all
contain the enzyme
lysozyme, which is capable
of breaking down the cell
walls of some bacteria
Lining of
trachea:
ciliated cells &
mucus
secreting cells
Nonspecific defense II
• 2nd line of defense
• Inflammation(Inflammatory response) characterized by
four symptoms—redness, swelling, pain, and heat; histamine released
causes blood vessels in the injured area to dilate,(redness)
which makes them more permeable to tissue fluid. Fluid that
leaks from the vessels helps the body destroy toxic agents and
restore homeostasis (swelling and pain,&heat)
Nonspecific defense V
• After a few days, infected
tissue harbors a collection of
live and dead white blood
cells, multiplying and dead
pathogens, and body fluids
called pus.
• Pus formation usually
continues until the
infection subsides.
• Eventually, the pus is
cleared away by
macrophages.
Swelling
occurs
Phagocytes
Tissue fluid moves
into injured area
Pus
Nonspecific defense III
• 2nd line of defense
Phagocytosis of
pathogens white blood
cells that destroy pathogens
by surrounding and
engulfing them.
• Macrophages are white
blood cells that provide
the first defense against
pathogens that have
managed to enter the
tissues.
Macrophage “eating” bacteria
Phagocytes
macrophage
bacteria
white blood cells that eat
macrophage
yeast
Fever
• When a local response is not enough
– full body response to infection
– raises body temperature
– higher temperature helps in defense
• slows growth of germs
• helps macrophages
• speeds up repair of tissues
Nonspecific defense IV
• Phagocytosis of pathogens
• If the infection is not stopped by the tissue
macrophages, another type of phagocyte,
called a neutrophil is attracted to the site.
• If the infection is not stopped by tissue
macrophages and neutrophils - Monocytes
Nonspecific defense VI
• Protective proteins:
• Interferons are proteins that protect cells
from viruses.
• Complement: help attract phagocytes to
foreign cells and help destroy foreign cells
• Natural Killer cells:type of white blood cell
that destroy the body's own infected cells,
may attack cells that form tumors
The lymphatic system
•
The lymphatic system becomes a
crucial battleground during infection
• a network of lymphatic
vessels and organs
– It returns tissue fluid to the
circulatory system
– It fights infections
• Lymph nodes are key sites
for fighting infection
– They are packed with
lymphocytes and
macrophages
Acquired Immunity
• Defending against a specific pathogen by
gradually building up a resistance to it
• This acquired immune response enables
these white blood cells to inactivate or
destroy the pathogen.
• Acquired immunity involves the production
of two kinds of immune responses:
antibody immunity and cellular immunity ~
• your 3rd line of defense
Acquired Immunity
• SPECIFIC IMMUNITY
• IMMUNE RESPONSE
a recognition system that distinguishes “self” from
“non-self”
• responds to foreign molecules called antigens
• Stimulates the body to make antibodies:
specific defensive proteins which help to counter
antigens in various ways
How are invaders recognized?
• Antigens
– chemical name tags on the surface of
every cell
• “self” vs. “invader”
one of your
own cells
antigens say:
“I belong here”
disease-causing
virus
disease-causing
bacteria
antigens say:
“I am an invader”
antigens say:
“I am an invader”
3rd line of defense
Lymphocytes ~type of white blood cell that carry
out the immune response
• Two kinds
– B cells secrete antibodies
that attack antigens
(antibody immunity)
– T cells attack cells
infected with pathogens
(cellular immunity)
B lymphocyte
B cells & antibodies
• B cells
– white blood cells that attack
invaders in blood
– mature in Bone marrow
• Patrolling B cells
– make antibodies against invader immediately
• Memory B cells
– remembers invader
– can make antibodies quickly the next time
• protects you from getting disease more than once
Antibodies
• Proteins made by B cells that tag invaders in the
blood so macrophages can eat them
– tag says “this is an invader”  gotcha!
• biological “handcuffs”
– antibody attaches to antigen of invader
invading germs tagged
with antibodies
B cells
releasing antibodies
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macrophage
eating tagged invaders
Antibody Immunity
• An antibody molecule
has antigen-binding
sites specific to the
antigen
• Do not posses the
power to destroy
antigens directly, tag
and mark them for
destruction by a variety
of mechanisms
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memory
B cells
“reserves
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10 to 17 days
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recognition
B cells
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release
antibodies
patrol blood
forever
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B cells
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(foreign antigen)
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invader
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B cells immune response
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T cells
• T cells mature in Thymus
• Helper T cells
– sound the alarm for rest
of immune system
• Killer T cells
– destroy infected body cells
• Memory T cells
– remembers invader & reacts against
it again quickly
Where’s that?
Attack of the Killer T cells
• Killer T cells destroy infected body cells
– T cell binds to invaded cell
– secretes perforating protein
• punctures cell membrane of infected cell
• cell bursts
Killer T cell
vesicle
cell
membrane
Perforin
punctures
cell membrane
cell
membrane
invaded cell
What if the attacker gets past
the B cells in the blood &
infects some of your cells?
You need trained assassins to kill
off these infected cells!
T
2006-2007
Attack
of the
Killer T cells!
Cellular Immunity
Infected cells
Pathogen
engulfed by
Macrophage
Displays antigens
on surface and
stimulates T cell
Perforin
Foreign
antigen
Infected cell lyses
Cytotoxic T cell
Attacks infected
cell
Stimulates
Helper T cell
Cytotoxic T cell
Immune response
invader
skin
invaders in body
invaders in blood
skin
invaders infect cells
macrophages
helper
T cells
B cells
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Y antibodies
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memory
T cells
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Y antibodies
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memory
B cells
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patrolling
B cells
T cells
killer
T cells
Passive and Active Immunity
• Acquired immunity to a disease may
be either passive or active.
Passive Immunity
Passive: short term,
antibodies passed on,
not stimulated by
antigens,
acquired naturally by
placenta or breast milk
or
artificially acquired by a
shot
Active Immunity
1. Active: long term,
conferred by actual
encounter with infection
(naturally acquired) or
vaccination *(artificially
acquired)
* vaccine~ substance consisting
of weakened, dead, ,or parts of
pathogen or antigen that when
injected , stimulates the
immune system
23.3 Noninfectious disorders
Section objective:
• Describe categories od
noninfectious disease
Noninfectious disorders
Genetic disorders
• Caused by the
inheritance of
genes that do not
function properly
• ex: sickle cell
anemia,
hemophilia, cystic
fibrosis
Noninfectious disorders
• Degenerative
diseases~ result of a
part of the body wearing
out ex: degenerative
arthritis
• Metabolic diseases~
results in an error in a
biochemical pathway
• Cancer~ abnormal cell
growth
DISORDERS OF THE IMMUNE SYSTEM
• Allergies are overreactions
to certain environmental
antigens called
allergens : Ex. Animal dander,
dust mites, pollen
release of histamine causes
symptoms: sneezing,
increased mucus production
in the nasal passages, and
redness.
Antihistamines can relieve
symptoms
DISORDERS OF THE IMMUNE SYSTEM
• Autoimmune diseases
immune system also
can mistakenly
attack the body’s
own tissues
– Examples: Rheumatic
fever, Type I Diabetes,
Multiple Sclerosis,
Rheumatoid arthritis,
Lupus
Rheumatoid arthritis
DISORDERS OF THE IMMUNE SYSTEM
HIV on a lymphocyte
• Immunodeficiency
diseases
– Immune components
are lacking, and
infections recur
Ex: Acquired immune
deficiency syndrome
(AIDS)
SCIDS
AIDS
– HIV (Human
Immunodeficiency
Virus) the virus that
causes AIDS
– HIV is transmitted
mainly
in blood and semen
– HIV kills helper Tcells and leads to
AIDS
Attacking transplanted tissue.
• T cells and antibodies also can attack
transplanted tissue, such as a transplanted
kidney, that comes from a source outside
the body.