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| Cytokines. |
Cytokines are chemicals released by cells that allow them to communicate with each other. Cyto means cell and kin- means kinesis or movement. These types of chemicals are released by one type of cell to call other cells to another area of the body. For instance, when there is an infection in your finger, the first cells on the scene will secrete chemicals that signal other white blood cells to come to their aid. They also are sensed in the hypothalamus and cause the body's thermostat to be reset to cause a fever which is another reaction natural reaction to microbes in the body. There are many different kinds of cytokines and more are being discovered all the time. There is a very active branch of biological research today that deals with cell to cell signaling. |
| Cytokines are small molecules that are released by cells to modify the behaviour of the surrounding cells. Cytokines play a major role in modulating the immune system. Among the large number of cytokines are the interferons, tumour necrosis factor and the interleukins. Cytokines are manufactured and released by cells of the immune system and perform a variety of functions including cell activation, inflammation, tissue breakdown and repair and cell death. Cytokines belong to a group of molecules called proteins. They are directly coded for in the DNA. Cytokines are relatively small proteins and often comprise of just a single chain of amino acids. A sub-group of cytokines are the chemokines. These attract more cells of the immune system and play an important role in the initiation of the inflammatory response. |
Amino acids are the building blocks of proteins. Put very simplistically, our genes tell our bodies which amino acids to put into the
proteins that we make, and it is the proteins that make up the significant constituents of our bodies. Myelin Basic Protein (MBP) is an
example of one such protein.
In order to understand how amino acids are glued together to make proteins, we must look at the DNA (deoxyribonucleic acid) that is
present in almost all the cells in our bodies.
DNA is built up of very many sub-units called neucleotides, each of which contains a chemical "base". There are only four different
bases and thus only four different nucleotides. The four bases are adenine (A), thymine (T), cytosine (C) and guanine (G).
Genes are sections of DNA, in which the neucleotides are viewed in groups of three called "triplets" or "codons". Each codon "codes"
for a particular amino acid. A gene is terminated by a stop code or terminator which is represented by one of three codons that do not
code for amino acids.
There are 20 different amino acids that are used in animals (there are others that are used in plants). There are 64 different codons
and most of the 20 amino acids are coded for by more than one triplet (see table below).
The process of synthesing amino acids from genes is known as transcription. During transcription, a gene is echoed from the DNA
into a complementary form called ribonucleic acid (RNA).
From the RNA, amino acids are produced and are joined with one another with a peptide bond. The resulting sequence of amino
acids is known as peptide string or polypeptide. Proteins are derived from these polypeptides.
proteins that we make, and it is the proteins that make up the significant constituents of our bodies. Myelin Basic Protein (MBP) is an
example of one such protein.
In order to understand how amino acids are glued together to make proteins, we must look at the DNA (deoxyribonucleic acid) that is
present in almost all the cells in our bodies.
DNA is built up of very many sub-units called neucleotides, each of which contains a chemical "base". There are only four different
bases and thus only four different nucleotides. The four bases are adenine (A), thymine (T), cytosine (C) and guanine (G).
Genes are sections of DNA, in which the neucleotides are viewed in groups of three called "triplets" or "codons". Each codon "codes"
for a particular amino acid. A gene is terminated by a stop code or terminator which is represented by one of three codons that do not
code for amino acids.
There are 20 different amino acids that are used in animals (there are others that are used in plants). There are 64 different codons
and most of the 20 amino acids are coded for by more than one triplet (see table below).
The process of synthesing amino acids from genes is known as transcription. During transcription, a gene is echoed from the DNA
into a complementary form called ribonucleic acid (RNA).
From the RNA, amino acids are produced and are joined with one another with a peptide bond. The resulting sequence of amino
acids is known as peptide string or polypeptide. Proteins are derived from these polypeptides.
Interleukins (also called lymphokines) are a sub-group of small soluable proteins called cytokines which function
as chemical messengers between cells. The role of interleukins is to mediate and control the immunologic and
inflamatory response. There are at least 18 known interleukins most of which have only been discovered in the
last few years. Their role within the immune system is only beginning to be understood and they are just starting
to be utilised in the treatment of a wide variety of diseases including cancer, AIDS and autoimmune diseases
such as multiple sclerosis and rheumatoid arthritis.
Interleukins are largely secreted by white blood cells (leukocytes) and received by receptors in others. The
stimulation of interleukin receptors causes the recieving leukocyte to behave in a variety of ways depending on
its type and the context. These include proliferating themselves, releasing other cytokines, inhibiting the release
of other cytokines and activating themselves.
The interleukins are abbreviated to IL- followed by their number, eg. IL-2. Their receptors are suffixed with an "R"
eg. IL-2R. The following table briefly describes the role of each of the known interleukins.
as chemical messengers between cells. The role of interleukins is to mediate and control the immunologic and
inflamatory response. There are at least 18 known interleukins most of which have only been discovered in the
last few years. Their role within the immune system is only beginning to be understood and they are just starting
to be utilised in the treatment of a wide variety of diseases including cancer, AIDS and autoimmune diseases
such as multiple sclerosis and rheumatoid arthritis.
Interleukins are largely secreted by white blood cells (leukocytes) and received by receptors in others. The
stimulation of interleukin receptors causes the recieving leukocyte to behave in a variety of ways depending on
its type and the context. These include proliferating themselves, releasing other cytokines, inhibiting the release
of other cytokines and activating themselves.
The interleukins are abbreviated to IL- followed by their number, eg. IL-2. Their receptors are suffixed with an "R"
eg. IL-2R. The following table briefly describes the role of each of the known interleukins.
An inflammation is a manifestation of the immune system's response to an invading organisms or substances.
These may be viruses, bacteria, fungi, allergens, or, in the case of autoimmune diseases, the bodies own tissue. A
typical example of inflammation that most people are familiar with is the painful red swelling associated with acne.
When an invading organism (pathogen) is first recognised the immune system launches a response involving a
number of different white blood cells (leukocytes) - this is known as an immune cascade.
At the site of the infection, there are a number of physiological changes that take place to assist the destruction of
the invaders. These include:
Increased blow flow to the area to maximise the number of leukocytes that can get to the infection site.
A thinning of the cells in local blood capillary walls (endothelial cells) to allow the leukocytes to squeeze through.
An increase in local temperature which has an antibiotic effect.
A large number of immune system signalling molecules (chemokines) are released by leukocytes to co-ordinate
the immune response and to call more leukocytes to the site.
In a skin infection, all these changes cause the hot, swollen and painful symptoms that we are all familiar with. The
pus that often results is the debris of dead bacteria, leukocytes and other cells.
Once the invader has been dealt with, the body terminates the immune response by killing off the leukocytes in the
locality. This is done by depriving them of nutrients (necrosis) and by making them commit suicide (apoptosis).
There are two ways that apoptosis happens:
by sending cells special cellular messenger molecules (cytokines) to tell them to die.
By not sending them other cytokines that tell them to keep living. A type of leukocyte, a helper T-cell, continues to
release this type of cytokine while it continues to detect the presence of the pathogen. Once it can no longer
detect it, it stops and other leukocytes die.
In multiple sclerosis and other autoimmune diseases, the inflammatory response seems to be launched in the
absence of a pathogen. It seems that certain T-cells are mistakenly recognising the insulating sheaths around
nerves (myelin) as a foreign invader.
These may be viruses, bacteria, fungi, allergens, or, in the case of autoimmune diseases, the bodies own tissue. A
typical example of inflammation that most people are familiar with is the painful red swelling associated with acne.
When an invading organism (pathogen) is first recognised the immune system launches a response involving a
number of different white blood cells (leukocytes) - this is known as an immune cascade.
At the site of the infection, there are a number of physiological changes that take place to assist the destruction of
the invaders. These include:
Increased blow flow to the area to maximise the number of leukocytes that can get to the infection site.
A thinning of the cells in local blood capillary walls (endothelial cells) to allow the leukocytes to squeeze through.
An increase in local temperature which has an antibiotic effect.
A large number of immune system signalling molecules (chemokines) are released by leukocytes to co-ordinate
the immune response and to call more leukocytes to the site.
In a skin infection, all these changes cause the hot, swollen and painful symptoms that we are all familiar with. The
pus that often results is the debris of dead bacteria, leukocytes and other cells.
Once the invader has been dealt with, the body terminates the immune response by killing off the leukocytes in the
locality. This is done by depriving them of nutrients (necrosis) and by making them commit suicide (apoptosis).
There are two ways that apoptosis happens:
by sending cells special cellular messenger molecules (cytokines) to tell them to die.
By not sending them other cytokines that tell them to keep living. A type of leukocyte, a helper T-cell, continues to
release this type of cytokine while it continues to detect the presence of the pathogen. Once it can no longer
detect it, it stops and other leukocytes die.
In multiple sclerosis and other autoimmune diseases, the inflammatory response seems to be launched in the
absence of a pathogen. It seems that certain T-cells are mistakenly recognising the insulating sheaths around
nerves (myelin) as a foreign invader.
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Leukocytes, also known as white blood cells, are the cells of the immune system. The role of leukocytes is to fight
infection by destroying the bacteria, viruses and other foreign organisms (pathogens) which are responsible for it.
They do this in a number of ways that can be broadly divided into the acquired immune system which recognises
specific invaders and the innate immune system which does not recognise specific invaders. In fact the two systems
closely interact with eachother and the division is far from total.
Leukocytes communicate with eachother and with other cells of the body via chemical messagers called cytokines.
All leukocytes originate in the bone marrow, though some are matured in other sites such as the thymus (T-cells)
and spleen.
Leukocytes divide up into five types within two classes:
Polymorphonuclear Granulocytes
Basophils and Mast cells
Neutrophils
Eosinophils
Mononuclear Agranulocytes
Monocytes (macrophages)
Lymphocytes (T-cells and B-cells)
infection by destroying the bacteria, viruses and other foreign organisms (pathogens) which are responsible for it.
They do this in a number of ways that can be broadly divided into the acquired immune system which recognises
specific invaders and the innate immune system which does not recognise specific invaders. In fact the two systems
closely interact with eachother and the division is far from total.
Leukocytes communicate with eachother and with other cells of the body via chemical messagers called cytokines.
All leukocytes originate in the bone marrow, though some are matured in other sites such as the thymus (T-cells)
and spleen.
Leukocytes divide up into five types within two classes:
Polymorphonuclear Granulocytes
Basophils and Mast cells
Neutrophils
Eosinophils
Mononuclear Agranulocytes
Monocytes (macrophages)
Lymphocytes (T-cells and B-cells)
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