ABO blood types
Here's a (relatively) simple explanation.The four basic types are A, B, AB, and O. These types are determined by which certain antigens, or protein markers, are found on a person's blood cells. A person can have 'A' antigens only, 'B' antigens only, both 'A' and 'B' antigens, or none.
Which (if any) of these antigens a person has is determined by genetics. In a person's genetic code, the gene pair that determines these antigens can be any combination of 'A', 'B', and 'O', making for six possible genetic sequences: 'AA', 'AO', 'AB', 'BB', 'BO', and 'OO'. The genes for 'A' and 'B' are codominant, and 'O' is recessive. This means that if a person's genes code for 'AA' or 'AO' their blood cells will carry 'A' antigens (this is blood type A), 'BB' or 'BO' will yield 'B' antigens (type B), 'AB' will cause both 'A' and 'B' antigens to be produced (type AB), and 'OO' will produce no antigens (type O).
Now for the important part: anti-A and anti-B antibodies. (Antibodies are one of the human body's defensive mechanisms.)
A person with type AB blood carries both 'A' and 'B' antigens, so neither type of antibody is produced. This is what makes type AB the "universal receiver"; because it has no anti-A or anti-B antibodies, it can accept any blood type.
Type A blood carries only 'A' antigens, so in this case only anti-B antibodies are produced, which will attack only cells with 'B' antigens; vice versa, for type B with 'B' antigens, only anti-A antibodies are produced.
Type O blood carries neither 'A' nor 'B' antigen markers, so both anti-A and anti-B antibodies are produced; if these antibodies encounter any blood cells that carry 'A' or 'B' markers, they will recognize those cells as foreign and attack them. For this reason, a person with type O blood cannot accept any other blood type; each of the other types (A, B, and AB) carries 'A' and/or 'B' antigen markers. However, for this same reason, type O is the "universal donor"; these blood cells, because they carry no 'A' or 'B' antigens, can safely mingle with any other blood type.
Those are the basics of ABO blood types in a nutshell. (Bonfils gave me a complimentary keychain; I might as well know about what goes on with the blood that I've been giving away.)
The good news is that my blood type (AB+) can accept every other known blood type. The less-than-great news is that my blood cells are only acceptable to other people with the same exact type, or only about 3.4 percent of the population.
Anyone, however, can use my blood plasma, because it contains none of the blood cells (with their pesky antigens and Rh factors) that cause the incompatibility.
This warrants some thoughtful consideration.
The process by which they (the nebulous conglomerate of licensed phlebotomists) collect plasma is called plasmapheresis. This involves several iterations of a cycle in which blood is collected and separated into its components in a centrifuge, the plasma is drawn off, and the remaining components are fed back into your bloodstream. The entire process (including paperwork, donation, and prescribed downtime) takes about an hour and a half, and most donation centers offer to "compensate" plasma donors for their time.
Plasma is a fairly versatile blood product. According to several informational websites, a bone marrow or organ transplant surgery requires over a hundred units of plasma. Plasma also contains proteins that are used to treat immunodeficiency and blood coagulation disorders (such as hemophilia); for these same reasons, it is also a sought-after material for biomedical research purposes.
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posted by the alygator @ 8:38 AM
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