Answer:
b) blastic red blood cell (RBC).
Explanation:
In excess of 340 blood group antigens have now been described that vary between individuals. Thus, any unit of blood that is nonautologous represents a significant dose of alloantigen. Most blood group antigens are proteins, which differ by a single amino acid between donors and recipients. Approximately 1 out of every 70 individuals are transfused each year (in the United States alone), which leads to antibody responses to red blood cell <u>(RBC) alloantigens</u> in some transfusion recipients. When alloantibodies are formed, in many cases, RBCs expressing the antigen in question can no longer be safely transfused. However, despite chronic transfusion, only 3% to 10% of recipients (in general) mount an alloantibody response. In some disease states, rates of alloimmunization are much higher (eg, sickle cell disease). For patients who become alloimmunized to multiple antigens, ongoing transfusion therapy becomes increasingly difficult or, in some cases, impossible. While alloantibodies are the ultimate immune effector of humoral alloimmunization, the cellular underpinnings of the immune system that lead to ultimate alloantibody production are complex, including antigen consumption, antigen processing, antigen presentation, T-cell biology.
