What blood type is characterized by the presence of only the A antigen?

The blood type characterized by the presence of only the A antigen is blood type A. This classification is based on the presence or absence of specific antigens on the surface of red blood cells. In blood type A, the A antigen is present, while the corresponding B antigen is absent.

People with blood type A have the gene responsible for producing the A antigen, and therefore, only express this antigen on their red blood cells. This distinction is crucial, as it determines compatibility for blood transfusions and organ donations. For instance, individuals with blood type A can receive blood from type A and type O donors, but transfusions from type B or AB blood types would trigger an immune response due to the presence of incompatible antigens.

Understanding blood type classification is essential in medical practice, particularly in transfusion medicine and for patients needing blood products. This knowledge also helps prevent adverse reactions in clinical settings.