Vampires and Blood Types
Originally posted to the VAMPYRES list by Nightingale

The following is provided for the use of any of our local writers of fluff who might wish to inject a little pseudo-science into their writing (possibly not many; there does seem to be some preference for more purely 'supernatural' vampyres upon this list). 

== SECTIONS ==

1. A simple review of blood types: what they are, and their clinical importance (with an obvious emphasis on transfusions!) 
2. The 'blood-sucking' model of vampyre physiology: 'My, Grandma, what big teeth you have! And what do you mean that we have to type- and cross-match before supper???' 
3. The 'blood-drinking' model of vampyre physiology: 'Of course you're my type, darling. . .*everybody* is my type! (Slurp, swallow!)' 

== I. Blood Types ==

Our body's immune system can be thought of as a nifty little defense mechanism designed to answer one question: is a given molecule part of us, or part of something else? For example, if I inject a *foreign* protein into an individual, that person's immune system will quickly recognize that protein as being 'non-self' and act to destroy it. On the other hand, the immune system is able to recognize the multitude of proteins that are native to that person's body as being 'self', and do not attack those.

 For a simple model of how a typical immune response might work, think back to the last nasty bacterial infection you had. The little invading bugaboo that made you so ill had proteins all over its cell surface. The proper term for these foreign proteins is *antigens*. Your immune system, upon recognizing that these antigens were 'non- self' then attacked the little bugaboo with (among other things) another type of protein called an *antibody*. These antibodies are able to recognize the specific foreign antigen. They (the antibodies) attach to the foreign antigen, which eventually leads to the destruction of the little bugaboo that made you sick.

 In terms of blood types, first note that our red blood cells have quite an array of proteins on their surface. The proteins we are concerned with here (and the ones by which we classify the most well- known of several blood group systems) are called the 'A, B, O' group of antigens. An individual who has the 'A' antigen on the surface of his/her blood cells is termed 'Type A'; likewise, an individual with the 'B' antigen on the surface of their blood cells is 'Type B'. If you should have inherited *both* the A and the B antigens from your parents, you are 'Type AB'. And if you have *neither* the A or B antigens on your blood cells, you are 'Type O'.

 A funny thing about blood. . .within a few months of birth we automatically get antibodies in our blood plasma against whatever blood antigens we don't naturally have. That is, someone who is 'Type A' will automatically have antibodies against the B antigen. Individuals who are 'Type B' have antibodies against the A antigen. Someone who is 'Type O' (remember, Type O has neither the A or B antigens on their blood cells) really hits the jackpot--they have antibodies that can attack both the A and the B antigens. 

 Blood transfusions are an excellent way to illustrate this system (though discussing this topic causes my fangs to descend--I'll try to stay calm). Let us say that you are Type A (you have the A antigen on your red blood cells, and the B antibody in your plasma). Oops! You scored in the danger zone on the vamp vulnerability test, and some list-member has snacked upon you! You need a transfusion, quick! Not thinking terribly clearly from your loss of Type A blood, you stumble into the evil Dr. Nightingale's laboratory and beg for help. 

 Unfortunately for you, Dr. Nightingale has terrible organizational skills, and has mislabeled a bag of Type B blood as Type A. . .and promptly infuses all of this Type B blood into your poor Type A body. The B antibodies in your plasma promptly start destroying all of the B blood cells that just got pumped into you (resulting in nasty things like blood clots going up to your already-befuddled brains). Worse still, since Dr. Nightingale gave you *whole blood* you have an additional problem: that bag of type B blood has A antibodies in the plasma, and those antibodies start attacking your native Type A red blood cells (more nastiness). Let us hope that your vampyric attacker transformed you, because at this point if you are not undead you are just plain dead.

== II. The 'blood-sucking' model of vampyre physiology ==

It would seem that there are two possibilities for how a vampyre feeds. One would be that he/she simply drinks the blood after opening a blood vessel. This blood would simply be digested in his/her vampyric digestive tract, and whatever mystery substance in that blood that the vampyre needed would be extracted. The other possibility (and the one addressed in this section) is that the vampyre takes the victim's blood directly into his/her cardiovascular system. 

 Let me propose a model for a 'blood-sucking' type of vampyre and then relate that model to blood types. We will assume that species *Vampyrus sanguinosuctioni* has hollow fangs that connect into his/her venous system, and note that veins have quite low blood pressure (about 7 millimeters of mercury) as opposed to high-pressure arteries (mean pressures of around 100 millimeters of mercury). A vampyre as a predator should be quick, silent and deadly. . .after all, it probably isn't a good idea to linger over a kill for several hours while risking some busy-body named Van Helsing coming along. Thus, for a kill, *V. sanguinosuctioni* would drive these hollow fangs into the victim's high-pressure carotid artery. 

 The pressure difference between the victim's artery and the vampyre's venous system would cause most of the victim's blood supply to enter the vampyres vascular system with extreme rapidity (a few minutes would be all that was required). If the vampyre wished not to kill, but rather to make a new vampyre, he/she would simply change targets from the carotid artery to the jugular vein. Since pressures would be about equal, instead of 'emptying' the victim, the vampyre would simply allow a few minutes of gentle 'mixing' of their respective venous blood, thus 'infecting' the victim.

 Relative to blood types, *V. sanguinosuctioni* would have some obvious problems to overcome. What if a Type A vampyre emptied a Type B victim? Unless some special mechanism is there to deal with this problem, our poor vampyre would end up like our late friend in the lab of Dr. Nightingale. I propose the following as one (of many possible) models for how the vampyre might get around the immune response problems:

1. One of the immediate effects of making a new vampyre is that the gene sequences that code for antigens A and B, if present, are *permanently* turned off. Thus, all vampyres would have Type O blood (neither the A or B antigen), and their red blood cells would thus be immune from attack by a victim's plasma antibodies. 
2. Normally, an individual with Type O blood would have both the A and the B antibodies in their plasma. A vampyre would have to have the ability to produce these antibodies turned off, so as not to have nasty clots of his victim's blood floating around in his blood stream. Thus, there *would* be a blood test to detect a vampyre. . .look for a Type O individual who lacks the A and the B antibodies you would normally expect. 

== III. The 'blood-drinking' model of vampyre physiology ==

A model of vampyrism where the vampyre simply drinks the victim's blood (*V. sanguinoslurpii*) into his/her digestive tract would eliminate (pardon the pun) any immune problems in feeding. However, this species of vampyre would probably suffer from chronic indigestion and heartburn. Another Malox Moment for poor *V. sanguinoslurpii*!