Immune System
Content
IMMUNE SYSTEM- THIRD LINE DEFENSE
DEFINITION
If a foreign agent penetrates the non-specific barriers, there is a third
line of defenceavailable – the specific immune response. The
specific immune response is a mechanism that is activated by the presence of
pathogens and foreign substances. These are known as antigens
ADDITIONAL NOTES
If a foreign agent penetrates the non-specific barriers, there is a third line of defence available
– the specific immune response.
The specific immune response is a mechanism that is activated by the presence of pathogens
and foreign substances. These are known as antigens. Even transplanted tissue from another
person, or parts of pathogens like the flagella of a bacterium, are recognised as antigens.
The body's immune system can determine which antigens are part of its own body structure.
These antigens are known as self-antigens
Non-self antigens
. These do not stimulate an immune response.
are the foreign substances that do stimulate an immune response.
The presence of a non-self antigen can trigger the production of specific proteins
called antibodies
. These are special proteins that are secreted by specific lymphocytes
and have a specific molecular shape that matches the molecular shape of an antigen. The
shape of the antibody gives it the ability to combine with and inactivate the antigen. When an
antibody combines with an antigen the result is an antigen-antibody complex (see diagram on
the right).
Pathogens contain certain chemicals that are foreign to the body and are called antigens.
White blood cells called lymphocytes carry a specific type of antibody - a protein that has a
chemical 'fit' to a certain antigen. When a lymphocyte with the appropriate antibody meets a
dangerous foreign body (pathogen containing antigen), the lymphocyte reproduces quickly,
and makes many copies of the antibody that neutralises the pathogen.
Antibodies neutralise pathogens in a number of ways:
They bind to pathogens and damage or destroy them.
They coat pathogens, clumping them together so that they are easily ingested
by phagocytes.
They bind to the pathogens and release chemical signals to attract more
phagocytes.
Lymphocytes may also release antitoxins that stick to the appropriate toxin and stop it
damaging the body.
PATHOGENS
A pathogen is anything that causes a disease.Pathogens include: Bacterium A group of
microscopic organisms that are capable of reproducing on their own, causing human disease
by direct invasion of body tissues. Bacteria often produce toxins that poison the cells they
have invaded.
DEFINITION
If a foreign agent penetrates the non-specific barriers, there is a third
line of defenceavailable – the specific immune response. The
specific immune response is a mechanism that is activated by the presence of
pathogens and foreign substances. These are known as antigens
ADDITIONAL NOTES
If a foreign agent penetrates the non-specific barriers, there is a third line of defence available
– the specific immune response.
The specific immune response is a mechanism that is activated by the presence of pathogens
and foreign substances. These are known as antigens. Even transplanted tissue from another
person, or parts of pathogens like the flagella of a bacterium, are recognised as antigens.
The body's immune system can determine which antigens are part of its own body structure.
These antigens are known as self-antigens
Non-self antigens
. These do not stimulate an immune response.
are the foreign substances that do stimulate an immune response.
The presence of a non-self antigen can trigger the production of specific proteins
called antibodies
. These are special proteins that are secreted by specific lymphocytes
and have a specific molecular shape that matches the molecular shape of an antigen. The
shape of the antibody gives it the ability to combine with and inactivate the antigen. When an
antibody combines with an antigen the result is an antigen-antibody complex (see diagram on
the right).
Pathogens contain certain chemicals that are foreign to the body and are called antigens.
White blood cells called lymphocytes carry a specific type of antibody - a protein that has a
chemical 'fit' to a certain antigen. When a lymphocyte with the appropriate antibody meets a
dangerous foreign body (pathogen containing antigen), the lymphocyte reproduces quickly,
and makes many copies of the antibody that neutralises the pathogen.
Antibodies neutralise pathogens in a number of ways:
They bind to pathogens and damage or destroy them.
They coat pathogens, clumping them together so that they are easily ingested
by phagocytes.
They bind to the pathogens and release chemical signals to attract more
phagocytes.
Lymphocytes may also release antitoxins that stick to the appropriate toxin and stop it
damaging the body.
PATHOGENS
A pathogen is anything that causes a disease.Pathogens include: Bacterium A group of
microscopic organisms that are capable of reproducing on their own, causing human disease
by direct invasion of body tissues. Bacteria often produce toxins that poison the cells they
have invaded.
