The Universal Blood Donor is o Since This Blood Type Lacks the A, B, and RH Antigens.

Blood Types 1 From the youngest to the oldest, every human being has blood coursing through his or her body. Blood works in the same way in every human body. It transports oxygen, nutrients, and antibodies around the body, warming up body parts as it circulates. It also carries waste and carbon dioxide away from body tissues. Though blood serves the same function in every person, people can have different types of blood. 2 Like eye color or other genetic traits, blood type is genetic. It is passed down from your mother and father. Certain combinations of blood types in parents result in certain possible blood types for children. You have no control over what type of blood you have, and there is no blood type that is better or worse when it comes to living a happy, healthy life. 3 The antigens in blood are what make the different blood types. The eight common blood types are determined by whether the blood contains or lacks certain antigens. Each person with a given blood type has the same blood antigens as other people with that blood type. Our bodies recognize the antigens in our blood and do not treat the antigens as foreign elements. However, if a person who is receiving blood in a hospital gets the wrong type of blood, his body will view the foreign antigens as invaders, and that person will have a severe reaction. 4 Two common antigens that are found on the surface of red blood cells are A and B. These determine the four major blood groups: A, B, AB, and O. In blood group A, only the A antigen is found in the red blood cells. In blood group B, only the B antigen is found in the red blood cells. Group AB has both the A and B antigens. Group O has neither the A nor B antigens in the red blood cells. Unit 3 1 Blood Types continued 5 There is a third antigen, the Rh factor, in addition to the A and B antigens. The Rh factor is either present (+) or absent (-). Each of the four main groups can be Rh positive or Rh negative. This makes the eight blood groups found in human beings: A+, A-, B+, B-, AB+, AB-, O+, and O-. 6 So, a person with A+ blood has A antigens in the red blood cells and also has the Rh factor. A person with A- blood has A antigens in the red blood cells, but does not have the Rh factor. Likewise for a person with B+ or B- blood. A person with AB+ blood has both A and B antigens in the red blood cells and also has the Rh factor. A person with AB- blood has both A and B antigens in the red blood cells, but does not have the Rh factor. A person with O+ blood does not have A or B antigens in the red blood cells, but does have the Rh factor. A person with O- blood does not have A or B antigens in the red blood cells and does not have the Rh factor. Matching Blood Between Donors and Recipients 7 2 Unit 3 Our immune system is responsible for keeping us healthy. If our immune system detects antigens that are not already in our body, it will react. The body will produce antibodies against the foreign antigens. To avoid this reaction, medical professionals must be very careful about matching blood from donors for blood transfusions. Group O blood can be given to anybody. It does not contain A or B antigens so there are no antigens for the recipient to form antibodies against. For this reason, Group O is called the universal donor. 8 Group A blood can be given to people with Group A or Group AB blood. Group A has the A antigen. A recipient who is also Group A already has the A antigen in his or her body. Group AB has the A and the B antigen. So, people with AB blood can also receive A blood since they have the A antigen already in their bodies. 9 Group B blood can be given to people with Group B or Group AB blood. People in groups B and AB already have the B antigen, so they can receive blood from someone in Group B without having their bodies react to a foreign antigen. 10 Group AB blood can only be given to other people with Group AB blood. If AB blood were given to someone with A blood, for example, the B antigen in the AB blood would cause the person’s body to attack the transfused blood. AB blood has both A and B antigens, so it can only be given to people who will not form antibodies against these antigens. However, people in Group AB can Blood Types continued receive blood from anybody. Their bodies are already used to both the A and B antigens. They are called universal recipients. 14 The Popularity of Blood Types 11 The most common blood type in the world is O+. This works well for hospitals that need donated blood to help patients, since type O blood is the universal donor. The blood type most often requested by hospitals is type O. 12 Interestingly, the percentages of people with certain blood types vary around the world. Type O, for example, is seen at a rate of about 63% around the world. In parts of Central and South America, however, the rate is close to 100%. Type B is a rarity. It is the least common blood type around the world. But, there are pockets of higher than average frequency in Central Asia. In fact, the lowest frequency of type O is in Eastern Europe and Central Asia. This happens to be where type B is fairly common. 13 The majority of people in the world have blood that contains the Rh factor. In some regions, nearly everyone has the Rh factor. But, even in the region with the lowest rate of Rh factor, the rate is still approximately 65%. No matter where you are in the world, more people will have the Rh factor in their blood than will not. Prevalence of blood types varies based on ethnic origin as well. Within the United States, type O+ blood is the most common. European Americans have the lowest prevalence of O+ blood, at 37%. This is compared with 47% of African Americans, 53% of Hispanic Americans, and 39% of Asian Americans. Blood type A+ is the second most prevalent for these ethnic groups in the United States. Components of Blood 15 Whole blood contains red blood cells, white blood cells, and platelets. Red blood cells carry oxygen from the lungs to the tissues of your body. They take carbon dioxide back to your lungs to be exhaled. Red blood cells move gases around your body. White blood cells are responsible for fighting infection and helping to heal wounds. They are an important part of your immune system. The third element of whole blood is platelets. The main function of platelets is to clot the blood. Platelets are much smaller than the other types of cells. They group together to plug holes in a vessel to stop bleeding. When you get a scab after scraping your knee, your platelets have done their job. 16 A complete blood cell count is a test that medical professionals do. It is probably the most common blood test, and is often done as part of a routine check-up. It measures the Unit 3 3 Blood Types continued size, number, and maturity of the different cells in a unit of blood. Doctors can use this test to determine if there are abnormalities with the production of blood cells. The number may also help a doctor determine if there is an infection. In these cases, the white blood cell count will often be elevated. 17 18 Patients receive blood in many modern medical treatments. Sometimes, they are given whole blood. Other times, they are given only the specific part that they may need. For example, a patient might only receive platelets to help with clotting. After blood has been donated, it is separated into its components. This means that for every blood donation, two or three patients may be able to benefit. When blood is given to a patient in a transfusion, the donated blood is matched by blood type. Then, only the specific parts of the blood that are needed are given. A patient might need red blood cells from type AB- blood, for instance. Or, a patient might need type B+ whole blood. Some patients may need a little blood, while others may need a lot. Blood Safety 19 4 Unit 3 Nowadays, it is safe for most adults to donate blood. (People under the age of seventeen are not allowed to donate.) The body quickly makes new blood to take the place of the blood that was given. It is also safe to receive blood. All blood donated in our country is carefully checked many times. It must be free of disease and appropriate to the patient who is receiving it. A division of the U.S. Food and Drug Administration (FDA) monitors the blood supply to make sure it is safe. 20 This is a technological advancement that benefits humanity as a whole. Before blood tests could identify blood type, doctors had no way of knowing if they were giving a patient blood that he or she could tolerate or not. Many patients received blood that they rejected. Their bodies produced antibodies to fight the antigens in the donated blood. This problem has largely been solved by modern medicine. In fact, blood transfusions save millions of lives in the United States every year. 21 Despite researchers’ utmost efforts, no blood substitute has been manufactured. There is simply no substitute for human blood. Blood is so complex and serves so many functions that it is hard to replicate. Researchers have been able to make a liquid that can carry oxygen, but it does not do all of the other things that blood does. It may be useful in some situations for a short period of time, but eventually matching blood will need to be found. This is why blood donations are so important. Blood Types continued 22 Blood is vital to human life. It serves many important functions in our bodies. Although there are different kinds of blood, they all transport oxygen to the body and carbon dioxide out of it, among other important things. It might be a good idea to know your blood type. Any adult who donates blood will find out his or her blood type. You may also want to ask your doctor about your blood type. Unit 3 5