Changes

These relate to blood cell types and can be available in any combination in a person. Thus, a person's blood may contain both type A and B cell types. They would then be classified as type AB. Having neither of these cell types indicates type O.

These relate to blood cell types and can be available in any combination in a person. Thus, a person's blood may contain both type A and B cell types. They would then be classified as type AB. Having neither of these cell types indicates type O.

Under the so-called ABO blood classification system in use for more than a century, Type O blood can be given to anyone, because it lacks such antigens. People with this blood type are known as ''"Universal Donors"'' and are much in demand by [[phlebotomist]]s. But Type A blood can only be given to people whose blood is Types A or AB, and Type B blood can only be used in those with blood Types B or AB. Type AB people are known as ''"Universal Recipients"'' as they can receive blood from any other blood type as well as their own, and each would be equally accepted<ref>[http://www.washtimes.com/national/20070404-122704-3244r.htm Washington Times article]</ref>

Under the so-called ABO blood classification system in use for more than a century, Type O blood can be given to anyone, because it lacks such antigens. People with this blood type are known as ''"Universal Donors"'' and are much in demand by [[phlebotomist]]s. But Type A blood can only be given to people whose blood is Types A or AB, and Type B blood can only be used in those with blood Types B or AB. Type AB people are known as ''"Universal Recipients"'' as they can receive blood from any other blood type as well as their own, and each would be equally accepted.<ref>[http://www.washtimes.com/national/20070404-122704-3244r.htm Washington Times article]</ref>

==Rhesus blood groups==

==Rhesus blood groups==