Which description correctly defines Type O blood?

Which description correctly defines Type O blood?

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

Answer: (A)

Type O is defined by having no A or B antigens on the surface of red blood cells and by having antibodies against both A and B in the plasma. This combination is what sets it apart from the other types: if red cells show A antigen, you’d have anti-B antibodies (Type A); if they show B antigen, you’d have anti-A antibodies (Type B); if both A and B antigens are present, there are no anti-A or anti-B antibodies (Type AB). The description that red cells lack A and B antigens and that the plasma contains antibodies against A and against B correctly captures Type O. For perspective, ABO-compatible considerations for red-cell transfusion are commonly taught with this pattern in mind; Rh status adds another layer, but the ABO pattern described here is the defining feature of Type O.

Type O is defined by having no A or B antigens on the surface of red blood cells and by having antibodies against both A and B in the plasma. This combination is what sets it apart from the other types: if red cells show A antigen, you’d have anti-B antibodies (Type A); if they show B antigen, you’d have anti-A antibodies (Type B); if both A and B antigens are present, there are no anti-A or anti-B antibodies (Type AB). The description that red cells lack A and B antigens and that the plasma contains antibodies against A and against B correctly captures Type O. For perspective, ABO-compatible considerations for red-cell transfusion are commonly taught with this pattern in mind; Rh status adds another layer, but the ABO pattern described here is the defining feature of Type O.