Why can type B red blood cells be destroyed in a person with type A blood?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Close-up illustration of multiple human red blood cells with their characteristic disc shape, floating against a red background. — blood group The major component of human blood is the red blood cell.

In the ABO blood group system, individuals with type A blood naturally possess anti-B antibodies in their serum. These antibodies are designed to identify and combine with the B antigens found on the surface of type B red blood cells.123

If type B blood is transfused into a person with type A blood, the recipient's anti-B antibodies recognize the donor's B antigens as foreign. The antibodies bind to these antigens, causing the red blood cells to clump together—a process known as agglutination—and subsequently burst, or hemolyze. This reaction, known as a hemolytic transfusion reaction, is dangerous and potentially fatal, which is why ensuring ABO compatibility is a fundamental principle of safe medical practice.1243