Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: ramitl on 16/07/2006 07:17:07
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Hello,
Sorry if this has been answered before.
I just wanted to understand how does the human body adapt to the DNA of a Blood/Organ donor? What happens to our genetic fingerprint? What changes?
Thanks in advance
Ramit
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I'm not an expert but
If you mean adapt in a way where the body accepts the transplanted organ then it doesnt the body will attack the organ just like any other foreign object which is why a person who has a transplant has to take drugs for the rest of their life in order to prevent their body from rejecting the organ.
A blood transplant contains no DNA at all, the parts which contain DNA the white blood cells are removed and all you receive during a transplant are the red blood cells which contain no markers from the doner.
With a bone marrow transplant i'm not 100% sure but i believe your body is going to be making blood belonging to someone else so apart from the legal problems i believe you need to take drugs to prevent the white blood cell from attacking the hosts organs.
Michael
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I don't know if the DNA is really relevant in transplants.
What the immune system goes after in a transplanted organ are markers on the surface of the cell that identify it as being alien to the body, not the DNA in the nucleus of the cell.
Donated blood can also cause problems, but less of them – this is why you have to make sure you match the donated blood to the donors blood type. On the other hand, blood is constantly being recreated, so the transplanted blood only needs to survive a relatively short time, whereas an transplanted organ may need to survive for decades, so even a small amount of rejection will cause some problems sooner or later (in fact, no matter how hard you try, all transplanted organs will suffer some rejection; one simply has to try and make sure it is as little as possible and as late as possible).
George
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Didn't I here somewhere that Transplants from new borns, or to them were less likely to need the rejection drugs or am I not remembering incorrectly!
DO either one of you remember reading something about that?
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A new born baby will not have a mature immune system, and so will not be able to mount an immune response to a transplanted organ, and so has no need of immunosuppressant drugs. Maybe someone will correct me on this, but I believe that by the time a new born is old enough to acquire an immune system it will have become used to any alien organ within its body.
Not sure that a new born would ever become a donor for an organ transplant (except maybe to another newborn), but stems cells from the placenta might well be used in some experimental medical procedures.
George
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Didn't I here somewhere that Transplants from new borns, or to them were less likely to need the rejection drugs or am I not remembering incorrectly!
DO either one of you remember reading something about that?
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A new born baby will not have a mature immune system, and so will not be able to mount an immune response to a transplanted organ, and so has no need of immunosuppressant drugs. Maybe someone will correct me on this, but I believe that by the time a new born is old enough to acquire an immune system it will have become used to any alien organ within its body.
Not sure that a new born would ever become a donor for an organ transplant (except maybe to another newborn), but stems cells from the placenta might well be used in some experimental medical procedures.
George
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Doesn't it only take a small piece of a liver to help someone? I thought that they could use a portion and not the whole liver!
Karen
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The liver is quite unusual as an organ because it has very little internal structure and is capable of regrowing, so you can divide in two a persons liver, donate one half to another person, and retain the other half for yourself, and both halves should regrow to complete livers. This has been done in many cases, but it still remains a very dangerous operation for both the donor and the recipient (although in the case of the recipient, the danger can be balanced out against the danger of not receiving a new liver).
George
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George, this is interesting as I have heard this before...how does it regrow into a full liver when this has been done and usually how long does it take? Why doesn't other organs do that?
"Lo" Loretta
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The liver is not the only organ that can regrow – the skin is also an organ, and that too can regrow.
I think the thing about the liver, like the skin, is that it has relatively little structure (the skin from one part of your body, while not identical to the skin everywhere else, is sufficiently similar that you can graft skin from one place to another and still expect it to function much as it should).
Don't know how fast the liver does grow – all I could find was that it was 'fairly quickly' – whatever that means.
George
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Something else I heard, was that the only stem cells in your body that regenerate themselves are in the nasal passages. They are doing stem cell research with them so that they don't have to resort to new born placenta ect. They think they might be able to use your own stem cells!I don't know all the details, but that sounds promising.
Karen
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karen
I also heard something along those lines .
Michael
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There are stem cells, and there are stem cells. There are many parts of the adult human body which may that may yield stem cells, but these stem cells are generally much less flexible than embryonic stem cells, and stem cells from the placenta and umbilical cord seem to lie somewhere between the two in terms of flexibility.
http://en.wikipedia.org/wiki/Adult_stem_cell#Types
quote:
Adipose derived adult stem cells
Adipose-derived stem cells (ASCs) have also been isolated from human fat, usually by method of liposuction. This cell population seems to be similar in many ways to mesenchymal stem cells (MSCs) derived from bone marrow. However, it is possible to isolate many more cells from adipose tissue and the harvest procedure itself is less painful than the harvest of bone marrow. Human ASCs have been shown to differentiate in the lab into bone, cartilage, fat, muscle, and might be able to differentiate into neurons, making them a possible source for future applications in the clinic.[8][9] In support of this, current studies in animals suggest that ASCs might be able to repair significant bony defects and ASCs have been recently used to successfully repair a large cranial defect in a human patient [1].
Haematopoietic stem cells
Main article: Pluripotential hemopoietic stem cell
Mammary stem cells
Mammary stem cells provide the source of cells for growth of the mammary gland during puberty and gestation and play an important role in carcinogenesis of the breast.[10] Mammary stem cells have been isolated from human and mouse tissue as well as from cell lines derived from the mammary gland. A single such cell can give rise to both luminal and myoepithelial cell types of the gland and has been shown to regenerate the entire organ in mice.[11]
Neural stem cells
The existence of stem cells in the adult brain has been postulated following the discovery that the process of neurogenesis, birth of new neurons, continues into adulthood in rats.[12] It has since been shown that new neurons are generated in adult mice, songbirds and primates, including humans. Normally adult neurogenesis is restricted to the subvetricular zone, which lines the lateral ventricles of the brain, and the dentate gyrus of the hippocampal formation.[13] Although the generation of new neurons in the hippocampus is well established, the presence of true self-renewing stem cells there has been debated.[14] Under certain circumstances, such as following tissue damage in ischemia, neurogenesis can be induced in other brain regions, including the neocortex.
Neural stem cells are commonly cultured in vitro as so called neurospheres - floating heterogeneous aggregates of cells, containing a large proportion of stem cells.[15] They can be propagated for extended periods of time and differentiated into both neuronal and glia cells, and therefore behave as stem cells. However, some recent studies suggest that this behaviour is induced by the culture conditions in progenitor cells, the progeny of stem cell division that normally undergo a strictly limited number of replication cycles in vivo.[16] Furthermore, neurosphere-derived cells do not behave as stem cells when transplanted back into the brain.[17]
Neural stem cells share many properties with haematopoietic stem cells (HSCs). Remarkably, when injected into the blood, neurosphere-derived cells differentiate into various cell types of the immune system.[18] Cells that resemble neural stem cells have been found in the bone marrow, the home of HSCs.[19] It has been suggested that new neurons in the dentate gyrus arise from circulating HCSs. Indeed, newborn cells first appear in the dentate in the heavily vascularised subgranular zone immediately adjacent to blood vessels.[20]
Olfactory adult stem cells
Olfactory adult stem cells have been successfully from the cells harvested from the human olfactory mucosa, the lining of the nose involved in the sense of smell.[21]
Adult stem cells isolated from the olfactory mucosa (cells lining the inside of the nose involved in the sense of smell) have the ability to develop into many different cell types if they are given the right chemical environment.
These adult olfactory stem cells appear to have the same ability as embryonic stem cells in giving rise to many different cell types but have the advantage that they can be obtained from all individuals, even older people who might be most in need to stem cell therapies.
Olfactory stem cells hold potential for therapeutic applications. Thanks to their location they can be harversted with ease without harm to the patient in contrast to neural stem cells.
http://en.wikipedia.org/wiki/Embryonic_stem_cell
quote:
Embryonic stem cells (ESCs) are stem cells derived from the inner cell mass of a blastocyst, which is an early stage embryo - approximately 4 to 5 days old in humans - consisting of 50-150 cells. Embryonic stem cells are pluripotent, meaning they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm. In other words, they can develop into each of the more than 200 cell types of the adult body when given sufficient and necessary stimulation for a specific cell type. When given no stimuli for differentiation, ESCs will continue to divide in vitro and each daughter cell will remain pluripotent. The pluripotency of ESCs distinguishes them from adult stem cells or progenitor cells, the latter two only having the capacity to form a more limited number of different cell types.
Because of their unique combined abilities of unlimited expansion and pluripotency, embryonic stem cells are a potential source for regenerative medicine and tissue replacement after injury or disease. To date, no approved medical treatments have been derived from embryonic stem cell research. This is not unusual for a new medical research field; in this case, the first human embryonic stem cell line was only reported in 1998.
http://en.wikipedia.org/wiki/Cord_blood
quote:
Umbilical cord blood is human blood from the placenta and umbilical cord that is rich in hematopoietic stem cells. Cord blood is collected after the umbilical cord has been detached from the newborn, and utilized as a source of stem cells for transplantation.
Cord blood stem cells are more proliferate and have a higher chance of matching family members than stem cells from bone marrow. Fathers have a 25% chance of matching their child's cord blood stem cells. Siblings have a 25% chance of being a perfect cord blood match.
George
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That is very interesting and I would like to keep up with this as I find it fascinating!
Karen
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I agree this is a very interesting subject.