What Are Blood Types, and Why Are They Important?

If your medical report reads A, Rh+, M, s, P1, Lua, K+, Kp(a-b+), Le(a-b+). Fy(a+), Jk(a+b+), don't run for a foreign language dictionary. The letters aren't Greek. They are simply the names given to various proteins that may or may not be present on the membranes of your blood cells. The proteins are grouped under names such as the Lutheran, Kell, Lewis, Duffy, and Kidd systems.

The most familiar blood proteins - and the first to be typed - are today known as the A-B-O blood groups. People with type A blood have the A protein (also called antigen) in their blood, but not the B. Type B blood means the B protein is present, but not the A. If both proteins occur, the type is called AB. Type O means neither protein is present. Another well-known blood protein is named Rh. If you are Rh+ (read R H positive), you have the protein. Rh- (read R H negative) means you don't.

In most cases, the presence or absence of these antigens means nothing in terms of health. The types are simply differences among healthy people. There are, however, exceptions. For example, it's not likely that you are missing both of the Duffy system proteins, Fy a and Fy b, unless you live in a country where malaria is common. In such countries, many more people have the Fy(a-b-) Duffy type. They enjoy a certain degree of immunity against malaria that people who are positive for either protein lack. Why? Because the organism that causes malaria, Plasmodium falciparum, uses the Duffy antigens to enter red blood cells. Without them, the malarial parasite cannot infect.

About the Author

Faith Brynie, Ph D

Faith BrynieFaith Brynie holds a B.A. in Biology from West Virginia University and an M.A. and Ph.D in science curriculum and instruction from the University of Colorado. She writes books and articles on science and health topics for children, teens, and non-scientist adults. Some of her books have won awards, including two 'Best Book of the Year' citations from the American Association for the Advancement of Science.