Download The immune system consists of a variety of white blood cells and

~----------------------------------------
The immune system consists of a variety of white blood cells and proteins that attack foreign invaders such as bacteria and
--.. viruses. This system is responsible destroying damaged cells, and irregular growths such as tumours. The immune system is
extremely smart and can distinguish between harmful and friendly organisms, and usually deals with these invaders without
any risk to human health.
~-Thymus
Bone' marrow
Spleen
-------
Lymph nodes
The human body is an ideal habitat for milltons of unseen organisms. The
body is kept moist, warm and well fed by our homeostatic systems. Inside
the body, bacteria, viruses and parasites are able to reproduce at
incredible rates and spread throughout the body or beyond in search of
new, favourable habitats. Due to their evolution, these organisms are able
to invade our defences and have adapted to live in a specific location of
our body,
Think about this ...the human body is host to more than 10000 times more
foreign cells than human cells!
You see it is a mutualistic relationship - we help out the bacteria, by providing it a nice safe and-warm place to live, arid in
return the bacteria helps us survive. For example, the bacteria Escherichia coli (E.co") lives.inside the large intestine of our
digestive sysiem and helps us absorb nutrients.
... ,
Not all invaders, are safe. Some strains of bacteria can be very dangerous. Prior to 1950, communicable disease, wasthe
most common cause of death. The use of antibiotics, vaccines, soap and laundry advancementshave helped to diminish this
risk, but the reprieve may be temporary, as many bacteria and viruses develop resistance (e.g.MRSA) and jump species
barriers (e.g.Swine Flu, Avian Flu).
Human Defences Against Invaders (Non-Specific Defences and Specific Immunity)
Immunity - is a term that we have all heard on survivor, but what does it really mean? Immunity is the ability to resist a
disease after being exposed to it in the past.
Non-Specific Defences - guard against a wide variety of pathogens (disease-causing agents).
> Effectiveness does not depend on previous exposure to the pathogen
> First line of defence against a pathogen is the skin. The skin provides a physical and a
chemical barrier. It is dry, and contains large amounts of tough, indigestible keratin. The oil in the
skin contains bactericides, and sweat forms an acidic layer that is inhospitable for microbial
growth.
> The linings of the respiratory system and the digestive system also are helpful in
preventing pathogen entry to the body as their mucus lining traps and sweeps away potentially
dangerous micro-organisms. The Hel inside the stomach kills the bacteria that lives on much of
the food that we eat.
> Non-specific defence also includes the "phage" family - macrophages, neutrophils, killer cells and monocytes
that kill bacteria by the process of phagocytosis (cell eating - whereby the cell ingests the bacteria and destroys it).
~
Macrophage: phagocytic cells found in the liver, spleen, brain, and lungs, they also circulate in the bloodstream and the
interstitial fluid.
Neutrophils: (white blood cells) neutrophils are one of first-responders of inflammatory cells to migrate toward the site of
inflammation, firstly through the blood vessels, then through interstitial tissue, following chemical signals. They are the
predominant cells in pus, accounting for its whitish/yellowish appearance. Neutrophils are recruited to the site of injury within
minutes following trauma and are the hallmark of acute inflammation.
Monocytes: leucocytes - white blood cells.
. 'c'"
The immune system consists of a variety of white blood cells and proteins that attack foreign invaders such as bacteria and
_viruses.
This system is responsible destroying damaged cells, and irregular growths such as tumours. The immune system is
extremely smart and can distinguish between harmful and friendly organisms, and usually deals with these invaders without
any risk to human health.
-'"---
Thymus
Bone marrow
Spleen
----
Lymph nodes
The human body is an ideal habitat for millions of unseen organisms. The
body is kept moist, warm and well fed by our homeostatic systems. Inside
the body, bacteria, viruses and parasites are able to reproduce at
incredible rates and spread throughout the body or beyond in search of
new, favourable habitats. Due to their evolution, these organisms are able
to invade our defences and have adapted to live in a specific location of
our body.
Think about this ...the human body is host to more than 10000 times more
foreign cells than human cells!
You see it is a mutualistic relationship - we help out the bacteria, by providing it a nice safe and warm place to live, and in
return the bacteria helps us survive. For example, the bacteria Escherichia coli (E.col!) lives inside the large intestine of our
digestive system and helps us absorb nutrients.·
'- ... ,
_
Not all invaders, are safe, Some strains of bacteria can be very dangerous. Prior to 1950, communicable disease, wasthe
most common cause of death. The use of antibiotics, vaccines, soap and laundry advancementshave helped to diminish this
risk, but the reprieve may be temporary, as many bacteria and viruses develop resistance (e.g:MRSA) and jump species,
barriers (e.g.Swine Flu, Avian Flu).
Human Defences Against Invaders (Non-Specific Defences and Specific Immunity)
Immunity - is a term that we have all heard on survivor, but what does it really mean? Immunity is the ability to resist a
disease after being exposed to it in the past.
Non-Specific Defences - guard against a wide variety of pathogens (disease-causing agents).
> Effectiveness does not depend on previous exposure to the pathogen
> First line of defence against a pathogen is the skin. The skin provides a physical and a
chemical barrier. It is dry, and contains large amounts of tough, indigestible keratin. The oil in the
skin contains bactericides, and sweat forms an acidic layer that is inhospitable for microbial
growth.
> The linings of the respiratory system and the digestive system also are helpful in
preventing pathogen entry to the body as their mucus lining traps and sweeps away potentially
dangerous micro-organisms. The Hel inside the stomach kills the bacteria that lives on much of
the food that we eat.
> Non-specific defence also includes the "phage" family - macrophages, neutrophils, killer cells and monocytes
that kill bacteria by the process of phagocytosis (cell eating - whereby the cell ingests the bacteria and destroys it).
_
.,
Macrophage: phagocytic cells found in the liver, spleen, brain, and lungs, they also circulate in the bloodstream and the
interstitial fluid.
Neutrophils: (white blood cells) neutrophils are one of first-responders of inflammatory cells to migrate toward the site of
inflammation, firstly through the blood vessels, then through interstitial tissue, following chemical signals. They are the
predominant cells in pus, accounting for its whitish/yellowish appearance. Neutrophils are recruited to the site of injury within
minutes following trauma and are the hallmark of acute inflammation.
Monocytes: leucocytes - white blood cells.
:.If''~'~
_.Jrr
~J~
_
-i~i~;-
r.(~''
Specific Defences - a variety of cells that recognize foreign substances and act to neutralize or destroy them. Over time,
and as a result of the variation in our genetic make-up, each of us develops an immune system unique in its capability to deal
with a wide variety of possible infections. We are not all exposed to the same diseases, and some diseases require a
stronger response than others. The specific immune system is primarily a function of the Iymphocytes of the circulatory
-------..
system,
Lymphocytes are specialized white blood cells formed in the bone marrow. They are divided into two specialized groups,
depending on where they mature. B Iymphocytes (B cells) mature in the bone marrow, andT Iymphocytes (T cells) mature in
the thymus gland, which is near the heart.
The Immune Response
The immune response is triggered by the entry of pathogens (bacteria, viruses, fungi, protists etc.) at
the site of infection.
1. Blood vessels dilate: Non-phagocytic leucocytes arrive at the site of infection and release histamine into the bloodstream
which .causes the blood; vessels to dilate. Dilatation causes the blood vessels to allow white blood.eelsto pass more readily.
Due to an increase in blood flow, the infected area become hot, red and swollen. The temperature-in your body at that site
increase to try to burn off or destroy the pathogen in aneffortto-maintain homeostasis .. ,:, l . "
.'
2: Phagocytosis occurs ~the macrophages eat and destroy the invading bacteria. The accumulation of dead rnacrophaqes
and bacteria is visible as pus at the site of infection.
JThe third line of defencebeqinsaner
a pathogen has been destroyed, the antigens from the patnogenthat· was eatenc
protrude from the cell wall ot.the macrophage,-'
l'
~
4. Helper T cells arrive - the receptor site on the surface of a helper T cells then binds to the antigen on the surface of themacrophage. The binding of the macrophage with the antigen onto the helper T cell causes the release of chemical
messengers from both cells. The chemical messengers cause the T cells to multiply. With a lot more helper T cells, it is
possible for the T cells to destroy and infected tissues breaking the tissue of the pathogen.
5. Antibody development - on the B cell, antibodies develop and bind to the antigens, contributing to the destruction ofthe
pathogens.
6. T and B cells unite - this causes the B cell to enlarge and divide which produces plasma cells and memory cells.
7. Plasma antibodies and memory cells - The plasma cells produce antibodies at a rate of 200 per second, and release
them into the bloodstream. Antibodies and memory B cells remain in the blood, ready to fight a new infection by the same
pathogen.
Summary of the Body's Defences
First line of defence (non-specific): skin, acid secretions of skin, lysozyme (enzyme in
tears, saliva, mucous secretions, perspiration), cilia (in respiratory passage), mucus, acids in
stomach.
.--.."
Second line of defence (non-specific): leukocytes - granulocytes, agranulocytes,
inflammatory response (swelling, heat, pain, redness)m relies on phagocytosis
completed by macrophages .
Third line of defence - Immune response (specific): Iymphocytes - T cells and B cells,
production of antibodies and memory cells to prevent infections in the future. ©
,~,,"
-.