Which blood type is characterized by the presence of only antigen B?

The blood type characterized by the presence of only antigen B is indeed Type B. In the ABO blood group system, blood types are determined by the presence or absence of antigens on the surface of red blood cells.

For Type A, the defining characteristic is the presence of antigen A, while Type AB has both antigens A and B present. In contrast, Type O has neither antigen A nor B. Therefore, for an individual to be classified as Type B, their red blood cells must exclusively express antigen B, with no presence of antigen A. This distinction is crucial for blood transfusions and compatibility, as the presence and absence of these antigens dictate how the immune system will react to foreign blood types. Understanding this classification helps in safe transfusion practices and avoiding hemolytic reactions in patients receiving blood.