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Author Topic:   Human Adaptation to Disease
Stagamancer
Member (Idle past 3261 days)
Posts: 174
From: Oregon
Joined: 12-28-2008


Message 1 of 14 (502135)
03-09-2009 8:46 PM


I've recently been interviewing for grad school, and at one of the institutions I visited, I had a very interesting conversation with a faculty member. We were talking about the evolution of disease in the face of all sorts of selection pressures: drugs, immune responses, other microbes, etc. During the conversation, we turned to talking about coevolution, and this faculty member brought up the point that it seems that the selection pressures involved in the "arms race" between a human host and a disease is fairly one-sided, i.e., our immune system forces our pathogens to adapt (in the evolutionary sense), but most of our immune system "adaptation" happens only at the somatic (physiological) level. By this, I mean that vertebrates have evolved an immune system that has the ability to generate countless numbers of antibodies and the like simply by rearranging and splicing genes within the immune cells. So, any immunity acquired by an individual is not passed along to his/her offspring, and the offspring much start as a completely naive host.

So, my hopefully discussion sparking questions are: Do you think that this is a generally accurate statement? And in terms of human (or more correctly-vertebrate) and pathogen interaction, do you think that we have evolved an adaptation that actually prevents any further evolutionary adaptation to disease?


Replies to this message:
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Message 2 of 14 (502190)
03-10-2009 9:32 AM


Thread moved here from the Proposed New Topics forum.

  
bluegenes
Member (Idle past 822 days)
Posts: 3119
From: U.K.
Joined: 01-24-2007


Message 3 of 14 (502508)
03-11-2009 7:53 PM
Reply to: Message 1 by Stagamancer
03-09-2009 8:46 PM


Stagamancer writes:

So, my hopefully discussion sparking questions are: Do you think that this is a generally accurate statement? And in terms of human (or more correctly-vertebrate) and pathogen interaction, do you think that we have evolved an adaptation that actually prevents any further evolutionary adaptation to disease?

I see what you mean, it is one sided, but I think the answer to your final question is "no". There seems to be variety in individuals (aids immunity, for example) and there's presumably nothing to stop new mutations making improvements in the immune system, and being selected for. Then there may be another factor on our side, so.....

Stagamancer writes:

....but most of our immune system "adaptation" happens only at the somatic (physiological) level. By this, I mean that vertebrates have evolved an immune system that has the ability to generate countless numbers of antibodies and the like simply by rearranging and splicing genes within the immune cells. So, any immunity acquired by an individual is not passed along to his/her offspring, and the offspring much start as a completely naive host.

.....here's something interesting. It may not be sure that somatic changes cannot be passed on. Vive Lamarck!!.

http://en.wikipedia.org/wiki/Edward_J._Steele

If there's anything in that, you can see the implications, and not just for immunity!

(Be sure to read the last 2 paragraphs - it returns to science after the bit about Steele's disputes).

Here's something else, going off at a bit of a tangent, but interesting.

Immune system may explain our small number of genes


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Stagamancer
Member (Idle past 3261 days)
Posts: 174
From: Oregon
Joined: 12-28-2008


Message 4 of 14 (502513)
03-11-2009 8:58 PM
Reply to: Message 3 by bluegenes
03-11-2009 7:53 PM


bluegenes writes:

There seems to be variety in individuals (aids immunity, for example) and there's presumably nothing to stop new mutations making improvements in the immune system, and being selected for.

True, we have some developed some recent adaptations to resist diseases. The example of the sickle-cell gene which confers resistance to malaria is the example that comes to my mind. Of course, this is a mutation that affects the red blood cells and the malaria parasite's ability to invade them. Do you know if aids immunity is caused by a mutation in the adaptive immune system, or to some other system or cells? Granted, either way this is adaptation to disease. I suppose I should have been more specific is asking whether or not it would be capable for the adaptive immune system to evolve resistance to disease. Your point about the possibility of Lamarckian evolution is intriguing and has some very interesting implications, especially immunity. However, I have a hard time imagining that this kind of thing would happen with enough frequency to be a significant mechanism for evolution. Though, if we could find a way to induce it ourselves, that would be pretty fantastic.


"There are three kinds of lies: lies, damned lies, and statistics."

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harry
Member (Idle past 3813 days)
Posts: 59
Joined: 03-15-2009


Message 5 of 14 (503121)
03-16-2009 8:41 AM
Reply to: Message 4 by Stagamancer
03-11-2009 8:58 PM


quote:
by a mutation in the adaptive immune system

I would guess so because that is what HIV attacks.


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New Cat's Eye
Inactive Member


Message 6 of 14 (503144)
03-16-2009 11:50 AM
Reply to: Message 1 by Stagamancer
03-09-2009 8:46 PM


So, any immunity acquired by an individual is not passed along to his/her offspring, and the offspring much start as a completely naive host.

I thought mothers pass on immunities (antibodies) through breast feeding.


This message is a reply to:
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Stagamancer
Member (Idle past 3261 days)
Posts: 174
From: Oregon
Joined: 12-28-2008


Message 7 of 14 (503147)
03-16-2009 12:19 PM
Reply to: Message 6 by New Cat's Eye
03-16-2009 11:50 AM


I thought mothers pass on immunities (antibodies) through breast feeding.

They may pass on some, but passing antibodies doesn't confer life-long immunity because the infant would not have memory B-cells making those antibodies. So they would confer some immunity until the antibodies passed by the mother have either degraded or bound to a pathogen and are all gone. In order to gain any real immunity, the offspring must have naive B-cells exposed to a pathogen in order for them to differentiate into memory B-cells that would then be ready the next time the pathogen invades to pump out more antibodies.


"There are three kinds of lies: lies, damned lies, and statistics."

This message is a reply to:
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Replies to this message:
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New Cat's Eye
Inactive Member


Message 8 of 14 (503373)
03-18-2009 10:40 AM
Reply to: Message 7 by Stagamancer
03-16-2009 12:19 PM


They may pass on some, but passing antibodies doesn't confer life-long immunity because the infant would not have memory B-cells making those antibodies.

What if they passed on antigens too? Do they? Wouldn't that do it?


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sfs
Member (Idle past 879 days)
Posts: 464
From: Cambridge, MA USA
Joined: 08-27-2003


Message 9 of 14 (503378)
03-18-2009 12:09 PM
Reply to: Message 1 by Stagamancer
03-09-2009 8:46 PM


There are mutations in at least five human genes (sometimes more than one such mutation per gene) that have been selected for because they provide resistance to malaria (HBB, SLC4A1, FY, G6PD and CD40L). Selection for resistance to other diseases is also likely, and is under investigation (e.g. a mutation in LARGE, which has been hypothesized to give resistance to Lassa Fever).

None of these cases involve the immune system. There undoubtedly has been pathogen-driven selection in immune-related genes, but it is difficult to tease out exactly what has been selected for, and why. In particular, selection has clearly occurred throughout the HLA region on chromosome 6, which contains a cluster of immune-related genes. Genetic variation is much higher there than elsewhere in the genome, and there is also evidence for recent incidents of selection for particular variants.


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Stagamancer
Member (Idle past 3261 days)
Posts: 174
From: Oregon
Joined: 12-28-2008


Message 10 of 14 (503380)
03-18-2009 12:18 PM
Reply to: Message 8 by New Cat's Eye
03-18-2009 10:40 AM


What if they passed on antigens too? Do they? Wouldn't that do it?

Yes, passing on antigens would do, that would effectively be giving the infant a vaccine, but don't think that that actually happens. That would be pretty cool if it did.


"There are three kinds of lies: lies, damned lies, and statistics."

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Taq
Member
Posts: 8207
Joined: 03-06-2009
Member Rating: 3.9


Message 11 of 14 (503388)
03-18-2009 1:19 PM


First off, good topic.

While the adaptive immune system is very crucial to human survival it is also important not to forget innate immunity. A very important mechanism is our Toll-like Receptors (TLR's). These are homologous to the immune receptors in species (e.g. Drosophila sp. where the proteins were first found) that do not have an adaptive immune system. These proteins are still very important in recognizing foreign invaders. I would strongly suspect that these proteins are under selection, as are the proteins in pathogens that the TLR's bind to. TLR's are just one example of the mechanisms involved in innate immunity. There are several more such as complement binding.

As to the question in the OP:

And in terms of human (or more correctly-vertebrate) and pathogen interaction, do you think that we have evolved an adaptation that actually prevents any further evolutionary adaptation to disease?

My answer would be no. The adaptive immune system is built on top of a very important innate immune system which is still under selection.

Edited by Taq, : No reason given.


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Dr Jack
Member (Idle past 450 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 12 of 14 (503389)
03-18-2009 1:31 PM
Reply to: Message 11 by Taq
03-18-2009 1:19 PM


The adaptive immune system is built on top of a very important innate immune system which is still under selection.

The adaptive immune system is also very much still under selection. Adaptive traits are still coded in genes, and the limits, means, and behaviour of their adaption can be varied by nature of these genes.


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Dr Jack
Member (Idle past 450 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 13 of 14 (505328)
04-10-2009 11:04 AM
Reply to: Message 1 by Stagamancer
03-09-2009 8:46 PM


Further to the topic, there's been some research done on the recent evolution of the human immune system: Selection & the innate immune system

Their work supports the view that the genetic basis of the immune system varies according to the local environment.


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Coragyps
Member
Posts: 5414
From: Snyder, Texas, USA
Joined: 11-12-2002
Member Rating: 6.0


Message 14 of 14 (505338)
04-10-2009 11:55 AM
Reply to: Message 4 by Stagamancer
03-11-2009 8:58 PM


Do you know if aids immunity is caused by a mutation in the adaptive immune system, or to some other system or cells?

The European mutation that helps resist HIV infection has to do with CCR5 receptors in T cells. Another pair of mutations has NK cells involved somehow.
http://www.news-medical.net/?id=40058

Those are innate immunity, right? It's been 40 years since I took biology.....


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