Download The Immune System and Disease

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Why do you get sick?
How do you get better?
What’s the best way for you to avoid getting
sick in the first place?
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For years, people thought diseases were
caused by curses, spirits, etc.
In the nineteenth century, Louis Pasteur and
Robert Koch concluded that infectious
diseases were caused by microorganisms
(germs) = the Germ Theory of Disease
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In the summer of 1975, many children in Lyme, CT developed
a rare form of childhood arthritis
Allen Steere realized the children developed their problems
after having a skin rash from a deer tick bite
Steere’s colleague, Dr. Burgdorfer, found an unusual spiralshaped bacterium in the ticks and the child patients
Steere injected lab mice with the bacterium and they
developed similar symptoms = Lyme Disease
So, Lyme disease is caused by a bacterium
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Koch developed a series of guidelines to identify the
microorganism that causes a specific disease
 1. The pathogen should always be found in the body of a sick organism
and should not be found in a healthy one.
 2. The pathogen must be isolated and grown in the laboratory in pure
culture.
 3. When the purified pathogens are placed in a new host, they should
cause the same disease that infected the original host.
 4. The injected pathogen should be re-isolated from the second host
and be identical to the original pathogen.
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Disease no longer seems unavoidable consequences, but
now pathogens could be identified and diseases could be
prevented or cured.
Section 40-1
No pathogen
Healthy mouse
Suspected
pathogen
Dead mouse
Injection of
organisms from
pure culture
Healthy mouse
Suspected pathogen
The pathogen
should always be
found in the body
of a sick
organism and
should not be
found in a
healthy one.
Dead mouse
Suspected
pathogen grown
in pure culture.
The pathogen
must be
isolated and
grown in the
laboratory in
a pure
culture.
Pathogen
When purified
pathogens are
placed in a
new host, they
should cause
the same
disease that
infected the
host.
Dead mouse
The very same
pathogen should
be reisolated
from the second
host. And it
should be the
same as the
original
pathogen.
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Disease = any change, other than injury, that
disrupts the normal functions of the body
 Diseases can be inherited (ex. Hemophilia)
 Diseases can be caused by materials in the environment
(ex. Cigarette smoke)
 Diseases can be produced by agents (ex. Bacteria, viruses,
fungi) = pathogens
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Pathogens = “sickness-makers”
Diseases caused by pathogens = infectious diseases,
because they enter, or infect, the body
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The human body provides great conditions for pathogenic
growth
You have many different microorganisms living in your body
that are actually harmless or beneficial
However, some microorganisms are dangerous
 Some bacteria break down body tissues and others release toxins
(poisons)
 Some protists, fungi, and worms are parasites that live inside you and
use up your nutrients or destroy blood/nerve cells
 Viruses are nonliving pathogens that use a host cell to make copies of
the virus and destroy other cells
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Infectious diseases are spread
 From person to person: coughing, sneezing, or
physical contact
▪ Common cold, mumps, measles, influenza, STDs (AIDS),
meningitis, athlete’s foot
 Contaminated water and/or food
▪ Cholera, dysentery, E.coli infection, salmonellosis
 Vectors: infected animals (ticks/mosquitoes)
▪ Lyme disease, malaria, West Nile virus, rabies
Section 40-1
Pathogen
Types
Viruses
Bacteria
Protists
Worms
Fungi
Chicken pox
Agent That Causes
Disease
Rhinovirus
Two types (A, B),
plus subtypes
Varicella
Measles
Paramyxovirus
Tuberculosis
Mycobacterium
tuberculosis
Neisseria meningitidis
Vibrio cholerae
Clostridium tetani
Trypanosoma
Disease
Common cold
Influenza
Meningitis
Cholera
Tetanus
African sleeping
sickness
Malaria
Amoebic dysentery
Schistosomiasis
Beef tapeworm
Athlete’s foot
Ringworm
Plasmodium
Entamoeba histolytica
Schistosoma
Taenia saginata
Imperfect fungi
Imperfect fungi
Method of
Transmission
Airborne; direct contact with infected person
Airborne; droplet infection; direct contact with
infected person
Airborne; direct contact with infected person
Droplets in air; direct contact with secretions of
infected person
Droplets in air; contaminated milk and dairy products
Direct contact with a carrier
Contaminated drinking water
Contaminated wound; usually puncture wound
Spread by tsetse fly
Spread by Anopheles mosquitoes
Contaminated drinking water
Freshwater streams and rice paddies
Contaminated meat
Contact with infected person
Exchange of hats, combs, or athletic head gear with
infected person
Drugs have been developed to use against
pathogens
 Antibiotics = chemicals that kill bacteria without
harming the cells of humans or animals
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 Penicillin = interferes with the synthesis of cells walls by
Eubacteria (breaks down peptidoglycan in their cell walls)
 Streptomycin = interferes with bacterial growth by
blocking protein synthesis in ribosomes
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Antivirals = inhibit the ability of viruses to invade
cells or multiply inside cells
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A series of defenses that guard against
diseases = body’s protection
Nonspecific defenses = “walls” of the immune
system keeping everything out
Specific defenses = “security guards”
identifying and inhibiting pathogens
Skin = most important nonspecific defense
 Physical barrier
 Acidic environment on surface kills bacteria
 Mucus, sweat, tears and saliva
 Traps pathogens and removes them from the body by cilia or destroys them
using the enzyme lysozyme, which breaks down cell walls
 Inflammatory response = reaction to tissue damage caused by injury or infection
 Blood vessels around wound expand, white blood cells enter infected tissue
and phagocytes (special WBCs) engulf and destroy bacteria, tissue becomes
swollen and painful, body temperature increases (fever) to slow pathogen
growth and increase circulation and activity of WBCs
 Interferon = proteins that “interfere” with the virus
 Proteins released by virus-infected cells to help other cells resist viral infection
by inhibiting viral protein synthesis, blocking viral replication
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Pathogen: any disease causing
agent
 Ex. Fungus, Bacteria, Virus etc.
 A series of specific defenses that
attack the pathogens = immune
response
 Antigen = a substance that triggers
the immune response (organic
molecules on the surface of
pathogens)
 Antigens are chemicals present on
the surface of viruses, bacteria,
pollen grains etc.
 Antibody = protein that helps
destroy pathogens by binding to
antigen and attracting phagocytes to
engulf and destroy them
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Phagocytes = engulf bacteria with amoeboid
motion
Lymphocytes = involved in immune response
 B cells = produce antibodies or immunoglobins
(secreted proteins specific to foreign molecules)
 Helper T cells = coordinate the immune response
 Killer T cells = directly kill cells that are infected
with intracellular pathogens.
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Immunity against pathogens in the body fluids
(blood/lymph)
Immunity produced by lymphocytes (type of WBC)
B lymphocytes (B cells) produce antibodies to mark
pathogens and prevent future infections
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Immunity that relies on lymphocytes (cells)
Killer T cells (cytotoxic T cells) can attack infected cells and
destroy their cell membranes
Killer T cells are what make organ transplants difficult,
because they see the new organ as foreign and begin to
attack it = rejection.
Here, the smaller cytotoxic T cell or Tc (arrow) is attacking and killing
a much larger virus-infected cell. The T cell will survive while the
infected cell is destroyed.
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People that survived infectious diseases, never developed
the same disease again
Memory B and T cells remain capable of producing specific
antibodies to that pathogen, ensuring the disease never gets
a chance to develop again
An immediate active immune response against the
pathogen in a vaccine
 Vaccination = injection of a weakened or mild form
of a pathogen to produce immunity
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 Prevents serious human diseases by stimulating the
immune system to create plasma cells capable of
producing the specific antibodies for another possible
infection
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Active Immunity lasts long term (permanent)
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Antibodies produced by other
animals for a pathogen are
injected into the bloodstream
 The antibodies will produce passive
immunity against a pathogen as long
as they remain in circulation (several
weeks)
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Antibodies from the mother are
passed to the fetus through the
placenta or to the infant in the
mother’s milk = maternal
immunity
 The antibodies will produce passive
immunity against most infectious
diseases for the first few months of life
or longer if breast-fed
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Although the immune system defends the
body from potential pathogens, sometimes
disorders occur
 The immune system may overreact to an antigen,
producing discomfort or disease
 The cellular nature of the immune response is a
potential weak point
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Overreaction of the immune system
Allergies occur when antigens from allergens (pollen, dust,
dust mites) bind to mast cells (type of immune cell common
in nasal passages)
Activated mast cells release chemicals = histamines, which
increase the flow of blood and fluids to the surrounding area
(sneezing, runny eyes/nose, etc)
Antihistamines = drugs used to reduce allergy symptoms by
counteracting the effects of histamines
Asthma = allergic reaction where smooth muscle
contractions reduce the size of air passageways in the lungs
making breathing difficult
The immune system has the ability to distinguish
“self” from “nonself”
 The immune system makes a mistake and attacks
the body’s own cells (“it attacks itself”)
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 Juvenile-onset diabetes (immune system attacks insulin-
producing cells in pancreas)
 Myasthenia gravis (attacks neuromuscular junctions)
 Multiple Sclerosis (destruction of myelin sheath – attacks
nervous system)
 Lupus (attacks cells and tissues resulting in inflammation
and tissue damage: heart, joints, skin, lungs, blood
vessels, liver, kidneys and nervous system)
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Pathogens are spread from person to person
by sexual contact
 Bacteria cause syphilis and gonorrhea
 Viruses cause hepatitis B, hepatitis C, genital
herpes, and AIDS
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Acquired Immune Deficiency Syndrome (AIDS) = when cells
of the immune system are weakened by infection
Caused by HIV (human immunodeficiency virus) and spread
by contact with body fluids (drug needles, unprotected
sexual intercourse, breast milk, blood during birth, blood
transfusions)
HIV attaches and destroys most helper T cells, so body is
more susceptible to infections
People DO NOT die from HIV/AIDS, they die from the
infections they get because the HIV virus has left their
immune system unable to respond to the infections
Section 40-3
Infection;
Immune
system
eliminates
most of HIV
Symptoms, such as
swollen lymph nodes,
are few
Loss of immune
function more
apparent; appearance
of characteristic
diseases such as
yeast infections
Almost
total loss
of cellular
immunity;
AIDS
Relative HIV
concentration
T cell
concentration
Years
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There are many different types of drugs being
used. Each drug has a different approach:
 Stop the virus from attaching to cells.
 Stop the virus from creating its protein coat.
 Stop the virus from replicating its genetic information.
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Doctors are now treating people with HIV with
drug cocktails (several different drugs at the same
time)
 These cocktails have dramatically increased the amount
of time people are living with HIV and their quality of life
– VERY expensive!
The number of people with HIV/AIDS has been decreasing.
Total population 2007: 6,625,000,000
Adults age 15-49 with HIV/AIDS, 2005 – 38 mill
New HIV infections, 2005 – 4.9 mill, 2007 – 2.5 mill
Adult HIV prevalence (%), 2005 - 1.1, 2007 – 0.8
Women age 15-49 with HIV/AIDS, 2005 – 17.5 mill
Children with HIV/AIDS, 2005 – 2.3 mill, 2007 – 2.5 mill
AIDS orphans (ages 0-17), 2003 – 15 mill
AIDS deaths, 2005 – 3.1 mill, 2007 – 2.1 mill
Source: http://hivinsite.ucsf.edu/global?page=cr-00-01
Viral RNA genome is converted to double-stranded DNA
by a virally encoded reverse transcriptase that is present
in the virus particle.
 Then the genome can be transcribed.
 Once the virus has infected the cell, two pathways are
possible:
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 the virus becomes latent and the infected cell continues to
function
 the virus becomes active and replicates, and a large number of
virus particles are liberated that can then infect other cells
 There are two types of HIV (HIV-1 and HIV-2)
 HIV differs from many viruses in that it has very high
genetic variability.
 This diversity is a result of its fast replication cycle,
with the generation of 109 to 1010 viruses every day,
coupled with a high mutation rate.
 This leads to many variants of HIV in a single
infected patient in the course of one day.
 This variability is compounded when a single cell is
simultaneously infected by two or more different
strains of HIV.
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Cells multiply uncontrollably and destroy healthy tissue
Cancer begins when cells lose the ability to regulate cell
growth and division
 Tumor: mass of growing tissue
▪ Benign: tumors that will not spread to surrounding tissue (non cancerous)
▪ Malignant: tumors that can spread to other tissues and organs invading
and destroying tissue (cancerous)
 Metastasis: the spread of cancerous tumors beyond their original site
to new places in the body
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As cancer cells spread, they absorb nutrients, block nerve
connections, and prevent proper functioning, disrupting the
body’s balance
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Cancer is caused by defects in the genes that
regulate cell growth and division
 Inherited genes
 Viruses: interfere with cell cycle (mitosis)
▪ Ex. Human papilloma virus (HPV: an STD) can lead to cervical cancer
or genital warts (non cancerous)
 Radiation: causes mutations in DNA
▪ Ex. X-rays, nuclear radiation, sunlight (UV Rays)
 Chemicals: cause mutations in DNA
▪ Carcinogens = chemicals that cause cancer
▪ Ex. Chloroform and benzene (industrial solvents used in production
of drugs, plastics and synthetic rubber, small component in
gasoline), cigarette smoke
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Prevention by protecting your DNA from agents that cause
cancer (not smoking, balanced diet with regular exercise)
Treatments
 Surgery: remove tumors to prevent spread of cancer
▪ Problem: cancerous tumors spread, so some cancerous cell may remain in
the body forming new tumors
 Radiation therapy: destroy cancer cells
▪ Problem: also damages healthy cells in the vicinity and there is a limit to
how much a person can have
 Drug therapy (chemotherapy): using chemicals to destroy cancer cells
or just stop the growth of cancer cells
▪ Problem: also damages healthy cells, uncomfortable side-effects
Section 40-4
The Study
of Cancer
includes a
knowledge of
Symptoms
Causes
which may
include a
including
Tumor
Viruses
Malignant
including
Chemicals
which may
consist of
which are
classified as
Benign
Radiation
Treatments
X-rays
Sunlight
Surgery
Nuclear
radiation
Drug
therapy
Radiation
therapy
Blood Type
of Donor
Blood Type of Recipient
A
B
AB
O
A
B
AB
O
Unsuccessful transfusion
Successful transfusion
Prentice Hall Biology Presentation Pro, 2002
Blood Types (review)
 Humans: 4 Main types classified by their antigens
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Type A:
Type B:
Type AB:
Type O:
A antigens
B antigens
A & B antigens
no antigens
B antibodies
A antibodies
no antibodies
A&B antibodies