Cytokines

What are Cytokines? Types of Cytokines The Science - How do Cytokines Work? Biotechnology and Cytokines Bibliography

What are Cytokines?

Cytokines play a crucial role in the immune system response to all kinds of disease. They interact with organs and cells, alone and in combination with each other. The diverse role that cytokines serve in the immune system make them an ideal target for intervening or bolstering immune responses. Using recombinant DNA technology cytokines can be created in a laboratory. They have many treatment applications including cancer, multiple sclerosis, anaemia, and rheumatoid arthritis.

Types of Cytokines

There are several types of cytokines with different varieties within each type. The following are the cytokines naturally produced by the body and the immune cells that produce them:

• Interferons (IFNs) have three main varieties. Produced by a number of immune system cells. Eg: White blood cells.
  
  
• Interleukins (ILs) have more than ten varieties. Produced by the white blood cells (leukocytes).
  
  
• Tumour Necrosis Factors (TNFs) have two main varieties. Produced by a number of immune system cells. Eg: T-Cells, white blood cells.
  
  
• Colony Stimulating Factors (CSFs) have many varieties and names. Produced by T-Cells and macrophages.
  
  
• Erythropoietin (Epoetin/EPO) has several varieties. Mainly produced by the kidney (10-15 percent originating in the liver).
  
  
• Thymopoietin has three main varieties. Produced by the thymus.

The Science - How do Cytokines Work?

Cytokines work in ways very similar to hormones. They are released by immune cells into the circulation or locally in a tissue. Cytokines interact with receptors on target immune system cells. This interaction triggers a cascade of biochemical reactions such as the release of other cytokines, cell division, or cell differentiation, that leads to a given event. Each type and variety of cytokine has distinct effects on specific targets:

• Interleukin 2 (IL-2) - This is the only variety of IL that is currently used therapeutically. It Interacts with T-cells that have been activated by an infection and triggers T-cell division increasing the number in circulation. IL-2 also stimulates the division of B-Cells and works in the bone marrow to promote the differentiation of stem cells into immune cells.

• Interferon - Has numerous therapeutic applications including:
  • Stimulating activity in other immune system cells,
  • Inhibiting growth in some types of cancer cells,
  • Increasing immune cell capacity to bind foreign particles,
  • Modulating the production of antibodies, and
  • Inhibiting viral protein synthesis, through a system of interactions.

• Erythropoietin - Stimulates stem cells in the bone marrow to differentiate into mature red blood cells.
  
  
• Colony Simulating Factors - Stimulate stem cells in the bone marrow to differentiate into immune cells called "neutrophils." Neutrophils are an important component of the body's inflammatory response to infection. CSF's can also stimulate activity in other immune system cells.

Cytokines can also work in combination to produce different effects in the body. Some therapies combine more than one cytokine to achieve their results.

Biotechnology and Cytokines

Therapeutic cytokines are produced through recombinant DNA techniques. The human gene that codes for the desired cytokine is inserted into a host cell, such as the bacteria species E-coli, yeast, or the cells of mammals or insects. The cells then act as factories, producing the desired human protein.

Proteins produced by non-human cells (like those produced through yeast or E-coli) will vary slightly from the those produced naturally in the body. Small variations in structure can cause therapeutic cytokines to behave differently from their natural counterparts. Therefore, recombinant cytokines are studied further to determine if they will behave differently due to the variations.

Bibliography

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