Individuals with Type O blood lack which of the following?

Individuals with Type O blood are characterized by the absence of both antigen A and antigen B on the surface of their red blood cells. The ABO blood group system classifies blood based on the presence or absence of these antigens. Since Type O blood has neither of these antigens, it is considered the universal donor type for red blood cells. This means that Type O blood can be given to individuals with any ABO blood type without causing an immune reaction, as there are no A or B antigens present to provoke an immune response.

In contrast, the Rh antigen, while it is an important factor in blood compatibility, is not specific to the ABO blood group classification. Type O individuals may still possess the Rh antigen, meaning they can be either Rh-positive or Rh-negative. Hence, the defining characteristic of Type O blood is the lack of both antigen A and antigen B.