Chapter 11 The Blood 337 Copyright Goodheart-Willcox Co., Inc. cells are classified as Rh-positive (Rh+) those who lack it are classified as Rh-negative (Rh–). The majority of people (approximately 85%) are Rh-positive. When writing out an ABO blood type with the Rh factor, drop the “Rh” and simply add a positive or negative superscript to the blood type. For example, a person who has the Rh factor and type AB blood would be described as AB+. Rh Classifi cation System Besides the antigens that determine blood type, there are other antigens on the surface of the red blood cells that determine the Rh factor. It is called the Rh factor because it was originally discovered in the rhesus monkey. Not everyone possesses the Rh factor. Those who have the Rh factor on the surface of their red blood The ABO Blood Group System Blood Type Erythrocyte (Red Blood Cell) Antigens RBC Antigens Antibodies Blood That Can Be Received AB A and B A B neither anti-A nor anti-B antibodies A, B, AB, O (universal recipient) B B anti-A B, O A A anti-B A, O O Neither A nor B No antigens anti-A and anti-B O (universal donor) Figure 11.14 © Body Scientifi c International Goodheart-Willcox Publisher Determining Blood Type Blood typing is a simple procedure performed in a laboratory or even as part of a classroom activity. The procedure can be performed in a matter of minutes. Blood typing involves a forward and a reverse typing. In the forward typing process, a person’s RBCs are mixed with a known chemical reagent containing only anti-A antibodies or only anti-B antibodies. If the blood cells clump together (agglutinate) in the sample with only anti-A antibodies, then it is type A blood. If it agglutinates in the sample containing only anti-B antibodies, then it is type B blood. If the blood agglutinates in both reagents then the blood is type AB. If no agglutination occurs, it is type O blood. The reverse typing involves a similar procedure. However, the person’s serum or plasma, rather than whole blood, is tested for agglutination. Clinical Application AJP/Hop Américain/Science Source In the ABO blood grouping system, the reaction of a blood specimen to various reagents determines its type.