Xenotransplantation, Biology

Xenotransplantation

Over the past 20 years transplantation of heart and kidney has become almost a routine in human but the availability of donors is the major limiting factor and there is a shortage of suitable organs for transplant and many patients die as a result. Transgenic animals can be developed as organ donors to meet this shortfall. Somatic cell cloning will improve the chances of success because it will allow animal to be produced in which the animal proteins responsible for rejection will be removed and replaced by human counterparts. Clones of transgenic bovine embryos and fetal dopamine cells were isolated and transplanted in a patient of Parkinson disease successfully; however, the real effect on recipient has yet to be confirmed. The fact that Dolly was cloned from a cell taken from an adult ewe shows that even specialized cells can be reprogrammed into all the cell types that make up an intact animal. Moreover, there is prospect of using the patient's own cells in such therapies.

The  transplantation of animal organs, tissues or cells into humans, xenotransplantation - is a major practical use to which gene knockout technology in large animals could be applied. Owing to its abundant supply, ease of domestication, anatomical and physiological compatibility, the pig has become the candidate species of choice. However, formidable barriers of cross species reject ion limit xenotransplantation, with the first major hurdle being the phenomenon of hyper acute rejection. The major cause of this rejection is the reaction of antibodies present in human blood to a carbohydrate, galactose-a-1, and 3-galactose. The structures or epitopes of this disaccharide that induce the immune reaction are present on the cell surface of most mammals but not in humans.

Gene knockout technology now opens up the possibility of deleting the a-1,3galactosyltransferase gene, which would allow the production of animals lacking this epitope. This and other targets relating to xenotransplantation has been a major driver to developing pig cloning technology. Concerns, however, have been raised over the possible risk of zoonoses, due to expression of porcine endogenous retroviruses. Gene knockout technology could be used to delete potentially active proviruses from the pig genome, although if there are a large number of active loci this may not be practicable. Nevertheless, if cloning can be made reasonably efficient in the pig, it will provide a method for cloning animals with the appropriate genetic modifications and minimum provirus load which would reduce any risk.

Unfortunately, bovine serum albumin that is synthesised in the liver is secreted across the mammary epithelium into milk. Bovine and human serum albumin is very similar and the high levels of the endogenous protein in the milk poses a problem for the purification of the human protein. One solution to this is to replace the bovine gene with its human counterpart. Thus, the bovine protein would be eliminated without compromising the animals' viability and, indeed, the secretion into milk of the liver- derived human protein would augment that produced in the mammary gland itself.

For the future even more ambitious types of genetic modification can be contemplated. Mice have already been generated in which the major immunoglobulin (Ig) gene families were deleted and replaced by the corresponding light and heavy chain human Ig families. Immunisation of these animals with specific epitopes generates monoclonal antibodies for diagnostic or therapeutic applications that can be produced by means of standard monoclonal antibody technology. Polyclonal antibodies, however, have a greater affinity and broader specificity for their target than monoclonals and, as such, are preferred for therapeutic applications. Notwithstanding the technical difficulties similar modifications in livestock could enable the bulk production of specific human polyclonal antibodies, and so take antibody production technology to the next stage.

Posted Date: 9/18/2012 7:59:53 AM | Location : United States







Related Discussions:- Xenotransplantation, Assignment Help, Ask Question on Xenotransplantation, Get Answer, Expert's Help, Xenotransplantation Discussions

Write discussion on Xenotransplantation
Your posts are moderated
Related Questions
Copper Copper is an essential trace element required for enzyme systems, iron metabolism, connective tissue metabolism, integrity of the central nervous and immune systems. Co

Q. Preservation of Tooth Structure? Fixed partial dentures have been considered the standard of treatment prior to advent of implant therapy. However, to obtain optimal esthe

Explain about the Gelation? Gelation refers to the process where denatured molecules aggregate to form an ordered protein network. Proteins can form a well-ordered gel matrix b

Q. What do you mean by Bleeding Index? This factor is applicable at this stage to evaluate the health of one stage implants in which the transmucosal component allows the forma

bone modeling may occur?

How might the destruction of large areas of tropical rain forest have world-wide consequences? As plants consume CO 2 during photosynthesis, extensive deforestation could resu

Define Swollen and Tender Joints and haemorrhage in various Tissues? Haemorrhages occur deep in muscle, particularly in calf, thigh, buttocks and forearm, causing pain in surro

Shapes of viruses Viruses occur in a wide variety of shapes. Some are spherical or polyhedral . Some are helical appearing cylindrical or rod-like and other are complex. Virus

Q. Therapeutic dose of pyridoxine? Therapeutic dose of pyridoxine (lg/day) is usually tried in all patients with hypermethioninernia and homocystinemia. For patients who do not

Q. What are yeast? Yeasts are unicellular fungi, which are widely distributed in nature. They are somewhat larger than bacteria. The cell length is about 10╬╝m and the diameter