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Codocyt

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Target cells, also known as codocytes, are red blood cells that have the appearance of a target with a bullseye. The cells have a dark center surrounded by a white ring and dark outer layer causing the cells to look similar to a target. Such cells are thin and have a disproportional increase in the surface membrane area to volume ratio. This increased ratio may result from an increase in membrane surface area or a decrease in hemoglobin content. Morphologically, target cells have a central, hemoglobinized area surrounded by an area of pallor. The periphery of the cell contains a band of hemoglobin.

Unrelated to the hematologic context (described above), target cell can also refer to a cell that is the target of hormone signaling. The word target cell first came about in to relationship to animal biology. Target cells are cells that have prearrange proficiency to react in a specific direction to a particular hormone signal. The word target cell first came about into relationship to animal biology. Target cells are cells that have a prearranged proficiency to react in a specific direction to a particular hormone signal.

There are many different types of hormones that circulate throughout the body in the bloodstreams. These hormones come in contact with almost all the cells in the blood and some will interact with one another. Even though the hormone does come into contact with the cells, they only interact and affect a certain amount of cells each time. These cells that are affected by the hormones are called target cells. The reason that some of the target cells do interact with a hormone is because the cells carry a receptor that the hormones need. When the hormones are mixed into the blood, they are carried throughout the bloodstream as a free hormone or a bounded hormone that can bind to plasm. If the hormone is free in the plasm then it will leave the bloodstream to an interstitial space somewhere in the body. As the free hormone levels increases in the blood, the more the hormones will leave to go to an interstitial space where they will bind to target cells. But if the free hormone levels decrease then less hormones will leave to an interstitial space, so therefore there will be a decrease in hormones binding to the target cells.

Target cells and Gene Therapy

Gene-therapy is a technique used for correcting defective genes that are responsible for the development of a disease. There are many techniques used by numerous researchers throughout the world. Some use a normal gene and insert it into a nonspecific location whereas others use an abnormal gene either to repair or swap for a normal gene. Most gene therapy studies use a so called normal gene and they insert that gene into the genome so that it can and most likely will replace the abnormal gene. The carrier molecule also known as vector must be delivered during gene transfer in the patient's target cells. However, the most commonly used vector is a virus, and it will have to be genetically altered so that it will be able to carry normal human DNA. In most human being they have target cells that are inside the liver and/ or lungs and can be infected by a viral vector. The vector has to do alot of work and unload genetic material that carries a therapeutic human gene into the target cells. Therapeutic genes restore target cells back to normal by help of a functional protein.


Cells may appear in association with the following conditions:

  • Liver disease: Lecithin cholesterol acyltransferase (LCAT) activity may be decreased in obstructive liver disease. Decreased enzymatic activity increases the cholesterol to phospholipase ratio, producing an absolute increase in surface area of the red blood cell membranes.
  • Iron deficiency: Decrease in hemoglobin content relative to surface area is probably the reason for the appearance of target cells. This is also seen in Thalassemias, Hemoglobin C disease, etc.
  • Post-splenectomy: A major function of the spleen is the clearance of opsonized, deformed, and damaged erythrocytes by splenic macrophages. If splenic macrophage function is abnormal or absent because of splenectomy, altered erythrocytes will not be removed from the circulation efficiently. Therefore, increased numbers of target cells may be observed.
  • Autosplenectomy caused by sickle cell anemia
  • Thalassemia (hemoglobinopathy)
  • Hemoglobin C Disease

Vorlage:Cell-biology-stub


References

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