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What's your type? Does it matter?

cmcgowan's picture

In the early1900’s, scientists discovered that humans have different 4 types of blood: A,B, AB, and O.  The distinctionsbetween these blood types are based on different carbohydrates and proteinsthat compose the cell membranes. Each of the different types produces different antibodies and antigens(1).  This system of classificationhas proven to be important because different properties make some blood typesincompatible.  For example, if aperson with Type B blood needed a blood transfusion or organ transplant, thedonation could not from a person with Type A or Type AB blood because Type Bblood makes antibodies to the antigen of Type A blood.  The donation could only come from adonor with Type B blood, or Type O blood. Type O blood produces no antigens, making it the “universal donor.” Thevarious rules that make certain blood types incompatible present a huge problembecause there are often shortages of donations. 

Althoughscientists have not yet figured out a way around this, they are gettingclose.  According to Time Magazine,one of the best inventions of the 2007 is a method that converts the otherblood types into Type O using bacteria (2). If this method proves to beeffective, will it no longer be necessary to distinguish between differentblood types? Even though we may no longer need to use this system ofclassification for blood transfusions and organ transplants, are there otherreasons why we might still need to know blood types?  My instinctive response to this question is yes. It seems tome that if different blood types exist, they must account for some biologicaldifferences between humans.  Ifthis is so, couldn’t knowledge of blood type then allow for specializedtreatment of these differences? Additionally, does blood type hold anysignificance in terms of human civilization? Is it possible that by looking atblood type we could learn more about human evolution and migration?

As I attempted tofind answers to my first question concerning biological differences, I cameupon an answer that also happens to relate to my second question.  According to many different sources,there is a relationship between blood types and susceptibility to differentdiseases, both infectious and non-infectious.  Each of the different blood types contains cells withdifferent characteristics. Certain characteristics and properties of thesecells make them more vulnerable to infectious diseases.  Scientists have found a major exampleof this in victims of the 17th -century plague by comparing bodiesof plague victims with bodies of those who died before the plague.  They found that those who had died as aresult of the plague were more likely to be of B blood type.  Scientists speculate that this has todo with the antibodies produced by Type B blood cells.  On the surfaces of plague bacterium,scientists have observed the presence of sugar molecules that are similar to Bmarkers.  For obvious reasons, TypeB cells do not make antibodies to Type B antigens. Therefore, those with type Bblood were less protected against the similarly looking Plague bacterium (3).

            Atthis point you may be asking yourself how this relates to my secondquestion.  My answer is this: eventhough blood types are determined by genetics, environmental factors (such asthe plague) play a role in determining which blood types are more likely tosurvive and reproduce.  It isimportant to note, however, that some blood types are predisposed to non-infectiousdiseases and conditions, including cancer and heart disease.  So although a certain blood type may bemore susceptible to a particular infectious disease, it is questionable whetherthis actually plays a larger role in evolution. Additionally, it is importantto point out that there is not one superior blood type overall.  While one blood type may haveproperties that increase risk for a certain disease, those properties aresimultaneously working to fight off other diseases (4).

            Ifone is more susceptible to certain diseases because of his/her blood type, itwould make sense to take preventative measures. Surprisingly enough, I wasunable to find many medical resources that suggested this. It is hard to knowif this is due to lack of attention or lack of belief.  I did find some information on a “bloodtype diet,” which suggests that different blood types interact with differenttypes of food differently. According to the Mayo clinic, however, there are nohealth benefits to this diet (5).

            Isknowledge of blood type beneficial in our quest to learn more about the humanrace?  Researchers suggest thatblood type provides an ideal way to learn about human variation withoutcultural prejudices. Patterns of blood type have been observed in different geographiclocations around the world (6). Blood type is also useful in learning abouthuman evolution in relation to other species. By comparing human blood typeswith other primate blood types, scientists can get an idea of which non-humanprimates we are closely related to. They can figure out common ancestors andlearn more about human roots in the whole scheme of evolution (7).

            Althoughblood type may no longer be significant when it comes to blood transfusions,there are many other reasons why this system of classification is stillrelevant and important. Blood typing gives us clues about human sickness anddisease, past populations, and our development as a species. As individuals wemay no longer need to know our own blood types, but blood types can tell usmany things about the larger picture.



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