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Chapter 17: The Human Immune System (ABO Blood types (ABO antibodies…
Chapter 17: The Human Immune System
Basics
Pathogens: Organisms that cause disease.
Germs are spread through physical contact, airborne contact (e.g. coughing), contaminated water/food, and infected animals.
Our body's immune system can fight in a
nonspecific
(attacking anything foreign) or
specific
(identifying invading cells) way.
Non-specific defence
First line of defence
Barrier that prevents pathogens from entering the body.
Skin
Mucous membranes
: Release mucous, trapping microbes.
Cilia
: In respiratory system. Sweeps out mucous containing microbes.
Stomach acid
: Kills germs that enter through nose + mouth.
Second line of defence
Limits the spread of invaders
before specific lines of defence kick in.
Inflammatory response
Characterised by swelling, redness, soreness, and increased warmth.
Histamine
Triggers
vasodilation
(enlargement of blood vessels).
Increases blood supply
to infected areas (bringing more nutrients and cells like phagocytes to fight invaders).
Also responsible for symptoms for the
common cold
(e.g. sneezing, redness of the eyes).
Results in
increased body temperature
--> faster immune system --> microbes find it harder to function.
Phagocytes
Engulf invading microbes.
Macrophages
(a type of white blood cell that extends
pseudopods
) can engulf large no. of microbes for a long period of time.
Interferons
Chemicals released to block
viral infections
.
Specific defence - Third line of defence
Consists of
lymphocytes
Circulate
in the blood, lymph, lymphatic tissue: Spleen, nodes, tonsils, and adenoids.
Originate in bone marrow.
2 types of lymphocytes.
Both recognise
specific antigens
(anything that triggers an immune response).
B Lymphocytes
Produce
antibodies
against a specific antigen.
Called a
humoral response
.
Remember: B for boost
.
T Lymphocytes
Fight pathogens in
combat
. Does not produce antibodies.
Called
cell-mediated response
.
Remember: T for take on.
Antibodies
Each antibody can only bind to
one specific antigen
and nothing else.
Antibodies
neutralise antigens
by
binding
to them -->
antigen-antibody complex
--> to be engulfed by phagocyte.
Clonal selection
Fundamental mechanism in the development of immunity.
Antigens bind to
T/ B lymphocytes
, which become
metabolically active
and
proliferates
(clones itself) and differentiate into
plasma and memory cells
.
Plasma cells
Fight antigens immediately (primary immune response).
Don't live long.
Memory cells
Also fight antigens.
Circulate
in blood in small no. for a lifetime.
Immunological memory
: Capacity of the immune system to generate a secondary immune response.
Mechanism that prevents you from getting a specific viral infection more than once.
Types of immunity
Passive immunity
Temporary
Antibodies are
borrowed
and don't survive long.
E.g. Maternal antibodies given to baby through placenta or breastmilk.
Colostrum
: The
first milk
a baby gets from its mother. Contains
100% antibodies
.
Active immunity
Permanent
You make antibodies yourself after
recovering from an illness/ after vaccine.
Vaccine
contains
dead/ alive viruses
to stimulate immune response.
ABO Blood types
ABO antibodies circulate the blood plasma and bind with ABO antigens in an improper transfusion.
It's dangerous for a recipient to have antibodies for the antigens of the donor.
Cross matching
is done to prevent this. (Where the two individuals blood samples are mixed in a lab to see if they match).
Blood O
: Universal donor because it contains no antigens that would trigger any other blood type to make antibodies.
Blood AB
: Universal recipient because even if it's triggered by A and B antigens, it will not produce any antibodies.
Blood is inherited and unchangeable.
4 blood types: A, B, O, AB.
Antigens are on the surface of red blood cells
and can trigger the body to make antibodies to fight against it if foreign.
Meaning of the table: Antigens are present, antibodies are not until triggered to be produced by another non-matching antigen. The table shows the antibodies produced if triggered.
AIDS Virus
Acquired immune deficiency syndrome.
HIV (human immunodeficiency virus)
attacks helper T cells
(which is a type of T lymphocyte that helped B lymphocyte make antibodies).
HIV -->
retrovirus
(viral RNA uses
reverse transcriptase
enzyme to make DNA and
integrate
(make part of) its own genome, like a reverse transcription.
Dangerous as it weakens the immune system, so the patient is vulnerable to diseases like cancer and infections.
Allergies, antibiotics, vaccines, and autoimmune diseases.
Allergies
Hypersensitive immune responses to
allergens
.
Response: Lots of
histamine
released.
Treatment:
antihistamines
.
Sometimes an acute allergic response leads to
anaphylactic shock
, which can result in death.
Antibiotics
Kill bacteria/ fungi.
Cures
the disease after a person is ill.
Vaccines
Prevent viral infections
.
There are no cures for viral infections.
E.g. Human papilloma virus vaccine to prevent cervical cancer.
Autoimmune diseases
When the immune system cannot properly tell apart itself and foreign things.
Perceives certain structures in the body as foreign and attacks them.
E.g. Multiple sclerosis, juvenile diabetes.
Treatment: Reduce symptoms by
suppressing the immune system
while also maintaining the body's ability to fight disease.
