Which antibodies are found in the blood serum of people with type B blood?

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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.

People with type B blood have anti-A antibodies in their blood plasma and serum.1

These naturally occurring antibodies are present despite no prior exposure to the corresponding red cell antigens. In the ABO blood group system, these antibodies serve to identify and combine with the A antigens found on the surface of red blood cells of other types, which typically results in agglutination (clumping) and destruction of the foreign cells.12