Which description correctly defines Type AB blood?

• A. Has both A and B antigens on red cells and no antibodies against A or B
• B. Lacks A and B antigens and has anti-A and anti-B antibodies
• C. Has A antigen only on red cells
• D. Has B antigen only on red cells

Answer: (A)

Blood type depends on which antigens sit on the surface of red blood cells and which antibodies are present in the plasma. Type AB has both A and B antigens on the red cells, and it has no anti-A or anti-B antibodies in the plasma. That combination means the cells display both marker types, but the plasma won’t attack those markers if exposed to A or B antigens from another source. This is why this description fits AB best: the presence of both A and B antigens on the cells and the absence of antibodies against A or B in the plasma. The other descriptions match other blood types: lacking A and B antigens with anti-A and anti-B antibodies describes type O; having A antigen only describes type A; having B antigen only describes type B.