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Comment by chimeracoder | Hacker News Reader

> At this point, my blood type changes to the blood type of my donor. And my blood will now have my donor’s DNA, not my own.

That's actually really fascinating. This perpetuates for life? This would seem to imply that a person who's received a transplant will, thirty years later, be walking around with two separate sets of DNA, as the other cells in the body presumably would not change.

Given that DNA is (indirectly) responsible for the way that cells communicate with one another (among other things), I wonder if this dichotomy creates any complications in other ways. (Not counting potential graft-host disease rejection - I'm talking about further down the line).

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I'm sure it does cause potential complications to an extent. However, I know of at least two comparable situations that occur without medical intervention:

1) Pregnant women -- During pregnancy, and to some extent afterward, the mother's blood contains cells from the fetus she is carrying. Some of these cells migrate to other places of the body. Scientists hypothesize that this is part of why pregnancy may lower cancer risk -- something about how the mother's immune system deals with these foreign cells. This is called fetal microchimerism. http://www.scientificamerican.com/article.cfm?id=fetal-cells...

2) Chimeric people. In rare cases, a human can be born that is made up of two separate DNA profiles. http://en.wikipedia.org/wiki/Chimera_(genetics)

>>http://en.wikipedia.org/wiki/Chimera_(genetics)

Completely off-topic: I feel more grateful for the access to Wikipedia after a blackout day.

Good luck, Amit, with your plan!

Just when you start to think that you've seen the weirdest/strangest/most amazing thing in nature, along comes something else that you wouldn't even begin to imagine was possible. Thanks for the Chimera link!

Yep, perpetuates for life. It's called Chimerism.

I'd be interested (obviously) in finding out what other implications this might have for me long term besides enabling me to life a life of crime. ;-)

I was gonna say, walking around with someone else's blood sounds like it'd make for an entertaining crime drama episode.

(SPOILER) this is the twist in a novel I've read:http://tinyurl.com/6r6hkhn (edit: tinyURL'd so the link text doesn't give tell you what the book is if you don't want to know).

CSI: LA did an episode about it in its earlier seasons. (As in, back when it was good.)

This might be the one: http://www.csiguide.com/episodedetail.aspx?csi=157.

Not CSI: LA but CSI, the one set in Las Vegas.

Yeah, I hit the A instead of the V, there. :)

While not a "crime drama", Chimerism is also the main diagnosis in an episode of House: http://house.wikia.com/wiki/Cane_%26_Able

Also in an episode of CSI (http://www.csifiles.com/reviews/miami/bloodlines.shtml)

There was an actual real-life crime episode involving that, look up Andrei Chikatilo, the police and a real trouble catching him because of mismatching blood types.

I'd give you a wikipedia link, but apparently I can't use google cache.

Actually, English wikipedia does not seem to mention that, and the Russian one says that not only Chikatilo did not have mismatched AB types of blood and sperm, but also that the condition has been proven to be genetically impossible (citing a broken link as a source for this statement, though).

Though not quite a crime drama, something like this has already happened. A woman trying to get a kidney transplant was informed that two of her sons couldn't be hers. Complications ensued. http://www.katewerk.com/chimera.html

Im sure CSI Miami have it covered.

Original CSI http://www.csifiles.com/reviews/miami/bloodlines.shtml

also, http://en.wikipedia.org/wiki/Genetic_chimerism_in_fiction

As a Forensic DNA Scientist, I can confirm this is indeed an issue.

I watched Gattaca again this weekend. This sure seems like a simpler option (assuming it affects the urine) than everything the main characters had to go through (collecting and storing blood and urine samples, making finger pouches for blood prick tests, etc.)!

Yes, my brother had a stem cell transplant using my stem cells. At one point a year after transplant he got some graft-vs-host disease and one of the first tests they do is a Chimerism test to see how much percent of his blood stem cells are actually mine. The way they do that is by comparing his blood to a base sample of mine. Or otherwise, they could compare his blood to his hair sample (which retains his old DNA), and see if its different. I'm obviously over simplifiying it, but as far as the crime situation some others are talking about on this thread, note that the identical footprint will only be in the DNA in blood. If you take skin/hair etc, it will still have the original DNA set.

As a total non-biologist, doesn't the "10/10" refer to the parts of the cells that touch and communicate? That is, the interface? If so, I would guess that what DNA is inside doesn't matter for the purpose of compatibility. Walks like a duck . . .

The central dogma of molecular biology is:

    1) DNA is transcribed to RNA
    2) RNA is translated into protein
    3) Proteins do work

(This is a gross simplification, but is still a good working model)

In this case, the 10/10 are probably cell surface markers, which are proteins in a specific conformation (with possibly some other types molecules attached). And yes, one of their roles is touching and communication. So the important part for compatibility is that the DNA that ultimately makes those proteins match Amit's DNA. After that, you have made a pretty good match, so you are then just hoping that they are healthy in all other regards.

To use a programming analogy, the 10 markers could represent an Interface definition. Amit's blood has that Interface, but the underlying class has a severe bug. The donor's blood has the same Interface, but has a better implementation.

The 10/10 match refers to HLA typing:

http://en.wikipedia.org/wiki/Human_leukocyte_antigen

These are the human MHC molecules that present antigen to T-cells. Unfortunately for the transplant process, a vast number of HLA alleles exist for each locus. This is important evolutionarily for population disease aversion, but makes the process of finding a match very difficult.

Central tolerance makes our immune system unreactive to self antigen. Foreign HLA present in tissue grafts will never be screened out by negative selection since this process requires expression of our own genes to cull any B or T cells that are self-reactive. Anything foreign will most certainly have reactive cell-surface epitopes (to varying degrees of reactivity).

Try reading up on central tolerance, somatic recombination, and clonal selection if you get the chance as it's a beautiful example of nature stumbling upon metaheuristic optimization:

http://en.wikipedia.org/wiki/Central_tolerance

http://en.wikipedia.org/wiki/Clonal_selection

http://en.wikipedia.org/wiki/V(D)J_recombination

To me, these are starker, more potent examples of biological optimization processes than evolution -- they're ongoing in your body right now.

I'm rather surprised that a bone marrow match wouldn't have the same blood type. I guess I shouldn't be though.

Edit: chimeracoder

Huh. :)

No, it is pretty surprising.

An interesting corollary of this is the possibility of curing AIDS[1]. Of course, the procedure is way to dangerous nor are there enough AIDS resistant donors for this become a viable cure, yet it is fascinating that these few people are one of the few that recovered from an incurable disease.

[1] http://www.time.com/time/health/article/0,8599,1858843,00.ht...

The dichotomy does seem to create complications, unfortunately:

Overall, 75% of AML transplant patients survive year one, 50% make it through year five.

Hmm. I don't think I've seen this as a twist/trope on TV procedurals yet.

After reading all this interesting discussion that your comment led to, I just now noticed your username :)

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