Antibodies: Evolution in action

I did a little experiment on the audience at FreeOK on Saturday (will be posted when The Thinking Atheist gets it up! Should be good quality, hes got all kinds of fancy stuff/tricks!).

*squint*

It wasnt really a matter of ‘will they get this?’, cause atheists/skeptics/freethinkers are smart.

It was more of ‘will they even like this?’

I *think* the answer to my experiment is “People kinda think this is cool!”

So Im gonna roll with it with you all– A series of posts connecting evolution (something a lot of skeptics are freaking amateur experts on) and immunology (scary) and the science of vaccines (scary). Connecting the new scary stuff to the stuff people are much more comfortable with, so skeptics can deal with anti-vaxers (and woo-ish immunology claims) as well as they handle Creationist claims.

One evolutionary feature that Creationists hate is gene duplication and divergence. Start with one gene. Accidentally make two of those genes. One of those copies can keep doin what it do, the other copy is free to ‘explore’. Sometimes the duplicated gene explores itself right into a tiger trap. And sometimes it figures out how to do something new, cool, and useful.

That is basically Your Immune System. A collection of gene duplications which diverged and learned new tricks (or became pseudogenes, or diverged to the point they left your immune system to do something else entirely). Your immune system is a beautiful example of evolution in action, which kinda makes me think Creationists use ‘THE IMMUNE SYSTEM IS PERFECTLY DESIGNED!’ for the same reason they used ‘HIV IS PERFECTLY DESIGNED!’: they dont know jack about what they are talking about.

A really easy example of this are the antibody isotypes.

When you think ‘antibody’, you probably think of a ‘Y’-like structure, like this:


i-df5e554dd262c76264370d16e38d606f-IgG-thumb-300x368-67998-thumb-200x245-67999.jpg(image altered from here)

Generic ‘antibody’. It can bind to bacteria or viruses or cancer cells or microscopic space monkeys from the Krelm nebula with each of the two shorter ‘Y’ arms. Hurray!

Except… things arent that simple.

Lets say you have An Antibody that recognizes a specific little chunk of the chicken pox virus. Thanks to gene duplication and divergence, you have that antibody in lots of forms!
i-c6c33f29c7448bf4a1341c9c67875656-Alltehantibodybutts-thumb-300x197-68000.png(image altered from here)

Its the same antibody (recognizes the same part of the same pathogen, with the same amino acid sequence), just with a different butt.

:-/

Each of these butts might kinda look the same, butt (heh) they all have their own specialties and deficiencies. Some do a bunch of jobs okay. Some do a few jobs REALLY well, butt (heh) suck at other jobs. And Im not sure why some of them exist outside of the fact we have no way of getting rid of wayward duplications that dont make themselves useful (Im looking at you, IgG4).

How do you get all of that antibody-butt variation?

For an example, just by chance alone, you have anti-chicken-pox antibodies in your body, before you were ever exposed to the chicken-pox virus or vaccine (another story for another day). Those basic anti-chicken-pox antibodies are actually that crazy ninja-star looking version, except sticking in the membranes of the cells that produce antibodies, B-cells!

When you are exposed to chicken-pox via a sick person or the vaccine, the B-cell that makes the anti-chicken-pox IgM gets messages via the antibody *in* its cell membrane, and starts to do things. Weird, unholy things. And I mean that very seriously– The B-cell starts to divide, and its babbys cut up their own DNA and paste it back together. This is an abomination. This should not happen (HELLO??? CANCER!!! We have a million safe-guards in our DNA to kill cells that start doing crazy stuff like CUT UP THEIR OWN DNA!!!), but in this case, it does, for a very good reason.

Because of gene duplication and divergence, there are lots of different antibody butt gene segments. When things get cut/pasted, this means some of the babby B-cells will make workhorse IgG antibodies. Some will make IgA antibodies, which can be secreted in your tears/saliva/mucus/etc, which will help protect you from getting chicken pox again if you ever share a drinking glass or a fork with a sick kid. And some will go off the deep end making IgE antibodies that are actually useful for something else entirely, but hey, the babby B-cells dont know that (Silly immune system! Chicken-pox isnt a parasitic worm!). Theyre just doing the best they can (youd be thanking them if you were exposed to a parasitic worm instead of chicken-pox).

So, thanks to evilution and evilutionary concepts like gene duplication and divergence, you can make the ‘same’ antibody lots of different ways. Because your immune system is mindless (its doesnt *know* you are infected with a *virus* and it needs to make antibodies good at attacking viruses), this ends up generating a lot of waste, like many evolved systems. But, because your immune system is mindless, it also means youve got a lot of bases covered when you are exposed to a new pathogen. And, the variants that are more helpful for a specific pathogen do survive better than the ones that arent overly useful (survival of the fittest w00t!)

Remember this stuff– more to come!

Bonus antibody info from We Beasties!

Comments

  1. #1 oriole
    August 2, 2011

    You’re a great explainer, Abbie. You make this kind of stuff clear even for non-biologists (I’m a mathematician by training, myself.) Much appreciated.

  2. #2 Justicar
    August 2, 2011

    Why is my immune system so prejudiced? It’s body-conscious about others who visit. I’ve tried to train it to be friendlier.

    Other than it’s the way it works, why do adjacent cells fail to attack these little fockers when they start vivisecting themselves? Isn’t that how cancer kind of works: cells start going crazy mad and making bunches and bunches of little friends for the party?

  3. #3 Brian
    August 2, 2011

    Yay, more science I just barely understand!

  4. #4 Zoonotica
    August 2, 2011

    Great explanation :)
    Looking forward to the next posts.

  5. #5 Connor
    August 2, 2011

    Great explanation again, gotta love the antibodies.

    I just saw this paper (http://www.ncbi.nlm.nih.gov/pubmed/17277123) recently where they show that antibody class switching – to a more effective type – can at least be altered via interactions with specific virus components via toll-like receptors. So, maybe our immune system has more of a ‘mind’ than was once believed.

  6. #6 dustbubble
    August 2, 2011

    Very clear even to a knuckledragger like me. Got a bit bamboozled by the “tiger trap”. The Wiki is straightforward enough, and I kind of think I know what the metaphor implies, but in the end I had to make up my own definition and it’s probably way off the mark.
    Mr Google is not my friend, as all I dredged up were recursive links to your good self, a spook-book and publicity for some,*ahem*, pop-tarts.
    Is there an official protein-wranglers’ definition of “tiger trap” (hopefully not involving goats, and chaps in khaki shorts)?

  7. #7 starskeptic
    August 2, 2011

    Science is SO COOL!

  8. #8 anderegg
    August 2, 2011

    when The Thinking Atheist gets it up!

    That’s what she said (badum tshh)

  9. #9 Kausik Datta
    August 2, 2011

    ERV:

    Its the same antibody (recognizes the same part of the same pathogen, with the same amino acid sequence), just with a different butt.

    That’s the best description of isotype switching, EVAH!!

  10. #10 Kausik Datta
    August 2, 2011

    IgG4 may look and feel useless, but recent evidence has emerged which implicates this subtype in immunomodulation that occurs in certain infectious diseases, especially parasitic and fungal diseases. Also, in experimental infection of mice with the yeast pathogen, Cryptococcus neoformans, human IgG4 (as also with IgG2) specific for the major antigen for this fungus promoted survival against a lethal challenge. There remains much in the IgG4 biology that isn’t understood yet.

  11. #11 Spence
    August 2, 2011

    Ah, yes, but you’re forgetting the wonderment of creationist logic.

    When the design is “perfect” (whatever that means), it is proof of design. Any imperfections subsequently found in said design, were put there by god to test our faith. Or something.

    Heads I win, tails you lose!

    Nice explanation though. I suck at biology, being forced to drop it for an arts subject early on in school because my curriculum was too science focused (stupid religious school), so it is awesome to have someone explain some of this stuff in an entertaining way.

  12. #12 Gurdur
    August 2, 2011

    This is actually a great idea, linking up evolution to immunology and vaccines. I’ll keep a close eye on developments in this.

  13. #13 Childermass
    August 2, 2011

    It is nice to see this issue re-injected. The Talk.Origins Archive did so a long time ago in an article that is largely forgotten:

    http://www.talkorigins.org/faqs/fitness/

  14. #14 Kevin
    August 2, 2011

    Damnit Abbie, I was going to write this post. Only not as good. And I probably wouldn’t have used the term “butt” (though I will from now on).

    I remember when I first took an immunology course, I thought VDJ and class switching were the coolest things ever. Then after studying immunology for several years, it started to be old-hat and boring. I’m only just starting to remember how cool it is.

  15. #15 jsfb
    August 2, 2011

    Excellent job and very cool. Love them babbies!

  16. #16 Rhology
    August 2, 2011

    So, thanks to evilution and evilutionary concepts like gene duplication and divergence, you can make the ‘same’ antibody lots of different ways.

    This concluding sentence could just as easily work with “intelligent design” in the place of “evilution” and “designed” in the place of “evilutionary”.
    Thus this piece is without any value in the ID-Darwinianismist debate.
    I’m kind of amazed this kind of stuff keeps getting put out there for that reason.

  17. #17 Guerra
    August 2, 2011

    So if you have an Auto-Immune distorter like Lupus, would that mean that the immune cells have ADD(whatever they call it now a days) and don’t listen to the body when it says its not infected anymore. So they keep attacking normal cells? A great video of some cells in . http://www.youtube.com/watch?v=JnlULOjUhSQ&feature=related

  18. #18 Kevin Crawford
    August 2, 2011

    Rhology,

    Behe used the complement system as an example of a system that was irreducible complex; if one protein in the chain isn’t present then the entire system couldn’t work. But genetic evidence shows that the compliment system was also developed by gene duplication. This means that before gene duplication the system still worked in some rudimentary fashion before the full system came into existence; it isn’t irreducibly complex. The same is true for antibody class switching. The easiest way to look at this is if a single protein has two activities. The gene for this protein could then duplicate and each gene could evolve to become better at each function separately. Over time it would appear that the two genes required each other to accomplish the two task function but it was original accomplished poorly by the single gene.

  19. #19 Rambleale
    August 2, 2011

    There there Rhology, you keep believing that if it helps keep the fear away. Meanwhile the informed world will keep on a turning.

  20. #20 Guerra
    August 2, 2011

    @Rhology

    If there was an “intelligent designer” who loved his children as the books say. Then why did he create bacteria, virus, and tumors that kill his children? Before you answer, don’t blame it on Lucifer.

  21. #21 Robert Blackburn
    August 2, 2011

    It was a great talk. Your delivery is inspiring and entertaining. It was a great addition to FreeOK

  22. #22 Tristan
    August 2, 2011

    I love this angle, and wish the “immune system — evolution” analogy was used more often. Can’t wait to read your take on affinity maturation – that’s like random mutation + natural selection in hyperdrive.

  23. #23 Rhology
    August 3, 2011

    Kevin and Guerra,
    Those are not responses.
    Kevin tried but swung at a different target.

    Guerra left the realm of science and is acting like he’s some sort of Pope of Morality. Sorry, Guerra, I didn’t see your badge and ID.

  24. #24 Kevin Crawford
    August 3, 2011

    >>Kevin tried but swung at a different target.< <

    I didn’t arbitrarily switch targets. I felt erv covered the argument for gene duplication being central to the evolutionary explanation of antibody class switching (butt transplant). However, I find the role of gene duplication in the evolution of the complement system easier to understand. Behe used clonal selection, V(D)J recombination and the complement cascade as examples of three irreducible complex biochemical systems. An evolutionary explanation for each of these systems is more than at least plausible (the minimum needed to refute Behe) but is highly likely; to such a degree that it is best to live as if it is a certainty.

    http://www.talkdesign.org/cs/evolving_immunity

  25. #25 Mobius
    August 3, 2011

    Abbie…

    So sorry I missed your talk in Tulsa. My car is broke. Would have liked to see you.

  26. #26 guerra
    August 4, 2011

    To quote my favorite movie. “We need no stinkin’ badges.”

    @Kevin, I was wondering what does an Auto-immunity disorder affects the process.

    @rhology
    P.S. I am not a scientist. I am an Artist and part time Judge, Jury, And Executioner of Morals.
    P.S.#2 Art and science are the same thing. Artist just don’t get the pay and the lab coats.

  27. #27 HC
    August 11, 2011

    just my humble thought, i think antibodies in humans evolve less sophisticated as what they should be. I bet caused by the food and the rapid changing environment of present world. Could have been the natural environment not been abused, human antibodies could have been more sophisticated — super gene missed

  28. #28 wwaalltt
    August 12, 2011

    Apostrophes! The new black.

  29. #29 charles soper
    August 17, 2011

    Shrew venom, gene duplication and the curse – happy reading,
    http://creation.com/images/pdfs/tj/j24_2/j24_2_3-5.pdf

  30. #30 charles soper
    August 17, 2011

    Before knocking down a straw man, it may be helpful to look at what your opponents actually publish about antibody production and gene duplication, here’s one recent creationist review of the subject.

    ‘The large discontinuity between the various means of generating immune system diversity in the animal kingdom makes it highly unlikely that one system could have evolved into another.’
    http://creation.com/immune-system-antibody-diversity

  31. #31 NJ
    August 17, 2011

    charles soper @ 30:

    Before knocking down a straw man, it may be helpful to look at what your opponents actually publish about antibody production and gene duplication

    Good point. Give us the citations to their peer-reviewed work in the scientific literature.

    {crickets}

    Oh, look, charles’ “straw man” turns out to be a highly accurate characterization of creationist dishonesty.

    Quel surprise!

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