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Captcha
06-10-2012, 03:21 AM
I have a prodigal son that I want to drag back into the family. It would be soap-style AWESOME if he could be a bone marrow transplant for his younger half sister, but what I'm reading suggests that it's pretty unlikely that he'd be a match. If they were full siblings the chances would be better, obviously, but that doesn't work for my plot.

Does anyone have any expertise in this? The two share a father - would it make the match more likely if the two mothers were from similar, possibly rare, genetic groups? Do genetic groups (assuming such a thing exists) tie in pretty closely with ethnicity?

Alternatively, is there any other family-dependent medical situation in which my prodigal would be needed? I guess all transplants probably have similar matching conditions? If not, please let me know! In general, I want something that will require a thirty-ish white male to be medically involved with his pre-adolescent half-sister (same father, different mother).

Thanks for any help!

lorna_w
06-10-2012, 03:39 AM
http://www.ucsfbenioffchildrens.org/education/types_of_bmt_donors/index.html

From what I just read (and it only took me ten seconds to google it), you need both sets of HLA (human leukocyte antigens) to match for a good transplant. Chances for a full brother or sister are only 25%. Chances for a half-sib are poor. one in a million according to one source, one in a thousand according to another.

Captcha
06-10-2012, 03:44 AM
http://www.ucsfbenioffchildrens.org/education/types_of_bmt_donors/index.html

From what I just read (and it only took me ten seconds to google it), you need both sets of HLA (human leukocyte antigens) to match for a good transplant. Chances for a full brother or sister are only 25%. Chances for a half-sib are poor. one in a million according to one source, one in a thousand according to another.

That's what I meant when I said the chances didn't seem good. I was hoping there might be a different medical condition with better chances?

Cath
06-10-2012, 04:54 AM
You know, one in a million still means that one out of every million is a match. That means about 300 or so folks in the US would be a good match for a sibling.

That the chances are poor doesn't mean they're impossible. Just acknowledge the stats and you can use it.

Captcha
06-10-2012, 05:24 AM
Yeah, if I have to, I guess I will. 'Cause it would REALLY fit well into the plot!

I was just hoping there was some other condition that might fit just as well without quite the same stretch of credibility...

lorna_w
06-10-2012, 06:13 AM
I looked at other transplants, and it seems pretty much the same, alas. go ahead and write it, if it works. Make everyone amazed at the match.

punahougirl84
06-15-2012, 01:27 AM
You might check out liver transplants - you can use live donors for partial liver transplants, and I think you just need to worry about matching blood type (went through this with my mom).

Mari
06-18-2012, 06:58 AM
i can talk to you about kidney transplantation.

Unimportant
06-18-2012, 08:37 AM
I have a prodigal son that I want to drag back into the family. It would be soap-style AWESOME if he could be a bone marrow transplant for his younger half sister, but what I'm reading suggests that it's pretty unlikely that he'd be a match. If they were full siblings the chances would be better, obviously, but that doesn't work for my plot.

Does anyone have any expertise in this? The two share a father - would it make the match more likely if the two mothers were from similar, possibly rare, genetic groups? Do genetic groups (assuming such a thing exists) tie in pretty closely with ethnicity?

Alternatively, is there any other family-dependent medical situation in which my prodigal would be needed? I guess all transplants probably have similar matching conditions? If not, please let me know! In general, I want something that will require a thirty-ish white male to be medically involved with his pre-adolescent half-sister (same father, different mother).

Thanks for any help!

A good explanation of how HLA works is here: http://www.stanford.edu/dept/HPS/transplant/html/hla.html

Basically, everyone has two sets of antigens. You get one set of antigens from your father, and one from your mother. Your half siblings could've inherited the same set from Dad, so they'd be a 50% match. To make them a full match, the guy's mum would've had to have his other set be identical to either the girl's mum or the girl's Dad. Unlikely, but not impossible. Me, I'd probably go with the latter and pick common haplotypes.

So, frex, if girl inherited A1 from Dad and A2 from Mum, she's A1,2. If he inherited A1 from Dad and A1 from Mum, he's A1, -. She has something he doesn't, but he doesn't have anything she doesn't. So he doesn't have anything her system will see as foreign and react to. If you make him homozygous for every HLA antigen -- rare, but possible -- and she carries those antigens as half of her HLA, then he'd be a perfect match for her.

Captcha
06-18-2012, 02:28 PM
A good explanation of how HLA works is here: http://www.stanford.edu/dept/HPS/transplant/html/hla.html

Basically, everyone has two sets of antigens. You get one set of antigens from your father, and one from your mother. Your half siblings could've inherited the same set from Dad, so they'd be a 50% match. To make them a full match, the guy's mum would've had to have his other set be identical to either the girl's mum or the girl's Dad. Unlikely, but not impossible. Me, I'd probably go with the latter and pick common haplotypes.

So, frex, if girl inherited A1 from Dad and A2 from Mum, she's A1,2. If he inherited A1 from Dad and A1 from Mum, he's A1, -. She has something he doesn't, but he doesn't have anything she doesn't. So he doesn't have anything her system will see as foreign and react to. If you make him homozygous for every HLA antigen -- rare, but possible -- and she carries those antigens as half of her HLA, then he'd be a perfect match for her.

Just a quick follow-up - if he WERE homozygous for every HLA antigen, would he be able to donate to everyone? Like, the equivalent of O negative blood? ('Cause that'd be cool!)

amschilling
06-18-2012, 06:14 PM
Just a quick follow-up - if he WERE homozygous for every HLA antigen, would he be able to donate to everyone? Like, the equivalent of O negative blood? ('Cause that'd be cool!)

Not sure about that, but what about having the two mothers be identical twins? That should cause them to have the same antigens, I believe. Plus think of the drama of Dad being with both twins... I can see a built in "ouch" factor that might have messed up the black sheep so that he's kinda got a reason to be what he is.

RozzandMaya
06-18-2012, 10:24 PM
I was once put on alert to provide a possible bone marrow match for one of my brothers. Since I'm a full sibling the doctors were reasonably confident that they'd find a match. With a half-sibling it would be more unlikely, but not impossible. What would be REALLY unlikely is finding a match from a total stranger.

And since recovery is several weeks for the donor and several months for the recipient, the prodigal just might have some time to reflect on why he was on the run from his family in the first place. Good luck with your prodigal!

Unimportant
06-19-2012, 01:31 AM
Just a quick follow-up - if he WERE homozygous for every HLA antigen, would he be able to donate to everyone? Like, the equivalent of O negative blood? ('Cause that'd be cool!)
Nope. There are a bunch of antigens at each locus. So at A, you get two out of something like 21 possibilities. At B, you get two out of forty-something possibilities. Same for C, DQ, DR, etc.

That's why the odds of his mother having the same set of antigens as his half-sister's mother are low....but not impossible.

Unimportant
06-19-2012, 01:36 AM
What would be REALLY unlikely is finding a match from a total stranger.
It does happen, which is why every potential recipient gets their HLA antigens tested and identified up front, and then donors (cadaver donors, donor banks, etc) get matched up with recipients as their organs become available.

Waaaaay back a zillion years ago, I worked in a transplant lab. I had my own blood tested just to check out some new reagents (we often used ourselves as guinea pigs). Then one day I was testing a whole slew of siblings for a man who needed a bone marrow transplant. None of his siblings were a match, but I kept staring at the patient's HLA numbers thinking "Gosh, that set looks familiar. Now, where have I seen...." D'oh! It was me! Turns out, I was a match for the patient!

I promptly contacted his doctor and offered to be a donor, and we started doing the additional tests to make sure I was compatible with him, but sadly he died before we could do the translant.