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interleukins

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.
 
The role of the interleukins
_Interleukin_ Secreting cells Action 
Interleukin-1
IL-1
Macrophages Stimulates T-cells to secrete interleukin-2 and activate the inflamatory response. It also causes the hypothalamus to increase the body temperature.
Interleukin-2
IL-2
Helper T-cells Causes activated T- and B-cells to proliferate themselves. It also induces antibody synthesis.
Interleukin-3
IL-3
T-cells Causes other leukocytes to be proliferated - it does this by making certain types of stem cell in the bone marrow to differentiate and grow. These stem cells (hematopoietic stem cells) mature into leukocytes.
Interleukin-4
IL-4
Helper T-cells Causes T- and B-cells to grow. It's also a factor in the production of IgE antibodies.
Interleukin-5
IL-5
Helper T-cells Stimulates B-cells, and eosinophils. It causes B-cells that produce IgA antibodies to proliferate 
Interleukin-6
IL-6
T-cells, 
Macrophages
Works in combination with alpha interferon to induce B-cell differentiation. It also causes the production of acute phase proteins in the liver and stimulates T-cells and other leukocytes.
Interleukin-7
IL-7
Stromal cells Causes lymphoid stem cells to differentiate into progenitor T- and B-cells.
Interleukin-8
IL-8
Macrophages, 
Endothelial cells
IL-8 is "sticky" for T-cells and neutrophils and helps to bring them to the site of an inflamation.
Interleukin-9
IL-9
  Induces growth in in Helper T-cells.
Interleukin-10
IL-10
T-cells, 
B-cells,
Monocytes
Macrophages
Acts to inhibit some aspects of the immune system while stimulating others. It represses the production of other cytokines within the immune system, especially gamma interferon, TNF-alpha, IL-1 and IL-6. It inhibits antigen presentation but activates B-cells.
Interleukin-11
IL-11
  Causes plasmacytoma cells to proliferate.
Interleukin-12
IL-12
Macrophages Causes T-cells and Natural Killer cells to proliferate.
Interleukin-13
IL-13
T-cells Promotes B-cell differentiation but inhibits inflammatory cytokine production.
Interleukin-14
IL-14
Dendritic cells,
T-cells
Enhances memory B-cell production and proliferation.
Interleukin-15
IL-15
  Enhances T-cell proliferation in the blood.
Interleukin-16
IL-16
  Acts as an adhesion molecule and activator for T-cells. Plays a part in both asthma and autoimmune diseases.
Interleukin-17
IL-17
T-cells Activates neutrophils.
Interleukin-18
IL-18
  Stimulates the release of Th1 cytokines.

Interleukin Links:
Interleukin
The Types And Functions Of InterLeukins In The Immune System
Interleukins
Interleukins: A group of bioactive proteins
Growth Factors and Cytokines


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