Transcript The Immune System

The Immune System
Biology
Chapter 41
• Pathogen-disease causing agent (various
types of bacteria, viruses, fungi, protists)
• Body uses both specific and nonspecific
defense mechanisms to prevent infection and
destroy pathogens
Nonspecific defenses
• Do not target a specific pathogen
1. Skin and mucous membranes (line
digestive system, lungs, nasal
passages)
Nonspecific defenses
2. Inflammatory response-suppress
infection and speed recovery. Injured
cells release Histamine which increases
blood flow to area bringing more white
blood cells (WBC’s). Also causes
swelling and redness in the infected area
Nonspecific defenses
3. Temperature response/Fever;
many bacteria do not grow well in
higher temps; however, too high a
fever can result in destruction of
important enzymes
Nonspecific defenses
4. Proteins:
• Complement system- proteins that circulate
in the blood and when they encounter a
pathogen they form a structure that ruptures
the cell membrane of the pathogen.
• Interferon- protein released by cells infected
with a virus, causes nearby cells to produce
an enzyme that prevents viruses from
making proteins and RNA.
5. WBC’s- most important counterattacks
carried out by 3 kinds of WBC’s
- Neutrophils-most
abundant type,
engulf and destroy
pathogens
- Macrophages-ingest
and kill pathogens,
concentrated
especially in spleen
and lungs
- Natural
killer cellsdestroy an infected
cell by puncturing the
cell membrane
causing water to rush
into the cell and burst.
One of the best
defenses against
cancer, can detect
and kill cancer cells
before a tumor
develops
Specific Immune Responses
• Cytotoxic T cells-attack and kill infected
cells
cytotoxic T-cell
tumour cell
• B cells- label invaders for later destruction
by macrophages
• Helper T cells- activate both cytotoxic T
cells and B cells
Two distinct processes work
together in the immune response
1. B cell response which is a passive,
humoral defense that aids in the removal
of pathogens
2. T cell response, an active, cell-mediated
defense that involves the destruction of
pathogens by cytotoxic T cells
Interactions Between Responses
• Antigen: Proteins or
other components on
the cell surface of the
pathogen. WBCs
have receptor
proteins that bind to
specific antigens.
• Antibody: Y-shaped
molecule produced by
plasma cells upon
exposure to specific
antigen
Immune Responses
Immune responses
Disease Transmission
• Person-to person contact
(contagious/communicable)
• Air
• Food
• Water
• Animal Bites
Koch’s Postulates: 4 step procedure for
identifying specific pathogens
1. Pathogen must be found in an animal
with the disease, not a healthy animal
2. Pathogen is isolated and cultured
3. Pathogen is injected into healthy animal;
animal must develop the disease
4. Pathogen taken from second infected
animal is cultured and it must be the
same as the original pathogen
Resistance to a disease is called
immunity
• Vaccination is a medical procedure used to
produce immunity.
• Edward Jenner developed a vaccine against
smallpox.
• A small amount of dead or modified pathogen is
injected into the body to produce an immune
response without symptoms of the infection.
• Your body develops antibodies and memory
cells against the pathogen (measles, polio,
tetanus, diphtheria, etc).
• Some pathogens have the ability to mutate
over time. The viruses produce new
antigens that your body does not
recognize (antigen shifting). That is why
you can get the flu, even if you have had a
vaccination or already had it before.
Disorders of the Immune System
1. Autoimmune disease-body attacks its
own cells (multiple sclerosis, rheumatoid
arthritis, Graves’ disease, Type I
Diabetes).
2. AIDS is caused by HIV (human
immunodeficiency virus). HIV invades
helper T cells causing them to produce
more virus and then die.
– HIV is transmitted through HIV-infected
WBC’s in body fluids and can be exchanged
through sexual contact and/or sharing of
needles
3. Allergic Reactions
• An allergy is the body’s overreaction to a
normally harmless antigen. Most allergic
reactions cause cells to produce histamines,
which cause swelling, redness, increased mucus
production, runny nose, itchy eyes and
congestion
• Most allergy medicines contain antihistamines,
which prevent the action of the histamine.
• Severe allergic reactions, like asthma and bee
stings, can be life threatening.