The evolution of blood

[Lucretia]

Tonight in micro-biology lab, we did blood typing, among other things.

Exactly what blood types are and how they are determined has been discussed before in several threads (I'm sorry, I don't know how to make links), but basically, it has to do with antibodies that most people have that attack other kinds of blood.

Some of the points in tonights lab were:

a) blood type antibodies are what are called "natural antibodies", that is, people are born with them or develop them without exposure to the substance the antibodies attack.

b)antibodies (of any kind) are extremely specific. Anti-A antibodies attack *only* type A blood antigens, nothing else, ditto for the other blood antibodies.

All of which made me wonder..why should this have evolved in people? What sort of survival advantage is conferred in being able to attack and neutralize some other sort of blood?

Presumable primitive man wasn't getting transfusions on a regular basis, and even if he was exposed to other peoples blood once in a while (injuries, birth, etc.) why should being able to destroy foreign blood (and only a specific kind of foreign blood, at that) be a trait that was selected for?




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Drink up, dear. I made it just for you.

sig by WallyM7

[Jois]

Should you be drinking in lab, dear?

IIRC all of us have this four type blood plan right back to Lucy and the apes. Can't figure out why we need more than one type of blood but it has turned out to be important because it is selected completely at random in the best Darwinian fashion.

Jois

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Are you driving with your eyes open or are you using The Force? - A. Foley

[bibliophage]

According to Human Genetic Diversity:

Some infectious disease organisms have ABO antigens on their cell walls, conferring some resistance on individuals who manufacture the appropriate antibodies, and increasing the susceptibility of people whose blood type matches the antigens

Antigens: Diseases
A: Syphilis, Smallpox
B: Infantile diarrhea, Typhoid fever (not typhus)
O: Bubonic Plague

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Work is the curse of the drinking classes. (Oscar Wilde)

[DrMatrix]

Good question. bibliophage's link gives a plausable answer - partial resistance to disease. But I thought that type O was the absence of A or B antigins, not the presence of an O angigen. If that is the case then how does Bubonic Plague exhibit the (non-existant) O antigen? Or is there such a thing as an O antigen?

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Virtually yours,

DrMatrix
If I've told you once, I've told you 0.99999999... times.

[Alphagene]

You're right, Doc. Type O is the absence of Type A and B anigens. I think the point the site is trying to make is that the absence of A and B antigens may confer an advantage against plague. For example, either antigen might be required for some aspect of the plague bacterium's metabolism. No A or B antigen would mean a "weaker" infection.

Just to confuse things, anarticle at britannica.com says:

Suggestions have been made that blood group O individuals are less susceptible to syphilis, group A to plague, and group B to streptococcal infections

I think this resistance information is based on disease prevalence in specific blood type populations. I doubt that any actual basic molecular biology has determined specific mechanisms of resistance based on ABO blood antigens.

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Tony Soprano: We're the only country in the world where the pursuit of happiness is guaranteed in writing... Where's my happiness then?
Dr. Melfi: It's the pursuit that's guaranteed.
Tony Soprano Yeah, always a fucking loophole.

[Lucretia]

Thanks for the info, guys. I hadn't realized that some disease microbes carried AB antigens (you are right, Dr. Matrix, there is no O antigen), as well as blood.


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Drink up, dear. I made it just for you.

sig by WallyM7

[bibliophage]

In response to an e-mail I sent asking about the type-O antigen mentioned in the table here, I received this response:

The structure of the antigens, the molecules attached to the red blood cell wall are given in the table below. The fact that we do not manufacture antibodies to the O substance does not mean that it does not have anypossible antigenic characteristics. You can see that the difference betweenthe three substances is only in the terminal group (missing in O). O A B -- Acetylgalactosamine GalactoseFucose-Galactose Fucose-Galactose Fucose-GalactoseAcetylglucosamine Acetylglucosamine AcetylglucosamineGalactose Galactose GalactoseAcetylgalactosamine Acetylgalactosamine Acetylgalactosamine

Best wishes,Dr. James R. Bindon, Ph.D.ProfessorDepartment of AnthropologyUniversity of Alabamajbindon@tenhoor.as.ua.edujbindon@simplecom.nethttp://www.as.ua.edu/ant/bindon.htm

From the library, I happen to have a copy of a book called The History and Geography of Human Genes by Cavalli-Sforza, Menozzi, and Piazza. Funny that I didn’t think of consulting it in regard to this question until today. Pages 126-129 deal with the ABO group. "The possible higher resistance of O individuals to syphilis has considerable interest because it might explain the near absence of A and B individuals in the Americas, except for Eskimos and some northern Amerind groups. In fact, it has been believed for a long time that syphilis was imported to Europe and the rest of the world from America after Columbus’s voyage in 1492."

To summarize the book’s data:

Type-A individuals are more susceptible to smallpox, malaria, throat cancer, and tuberculosis, but less susceptible to influenza.

Type-O individuals are more resistant to diabetes, pernicious anemia, myopia, rheumatic heart disease, thrombosis, embolism, cirrhosis of the liver, syphilis, plague, cholera, infant diarrhea, and cancers of the mouth and esophagus, malaria . They are more susceptible to ulcers and rheumatoid arthritis, influenza, and smallpox.

Type-B is less susceptible to smallpox and tuberculosis. More susceptible to throat cancer.

The strongest association is with myopia. Type-A and type-B individuals are 2.5 times more likely to be myopic than type-O. The others diseases are associated with only a 5% to 50% increase in incidence. It’s interesting to note that Native Americans, mostly type O, were hit very hard by smallpox epidemics. The death rate was near 90% in some cases. The high incidence of diabetes among Native Americans would seem to anomalous.

The relative incidence of A, B and O can evidently change quite readily over time. Using only the ABO system, it would be predicted that Icelanders are more closely related to the Irish and Scots than to Norwegians, in contradiction to the historical record. Other genetic evidence has recently proven Icelanders are most closely related to Norwegians, next are the English, with Scots and Irish not very close.

[bibliophage]

The table didn't translate well. Let's try this (if anybody cares):

O: -- Fucose-Galactose Acetylglucosamine Galactose Acetylgalactosamine

A: Acetylgalactosamine Fucose-Galactose Acetylglucosamine Galactose Acetylgalactosamine

B: Galactose Fucose-Galactose Acetylglucosamine Galactose Acetylgalactosamine