Ace the Harr ISBB Exam 2025 – Unleash Your Inner Immunology Pro!

In the context of a transfusion for an AB-positive baby with Hemolytic Disease of the Newborn (HDN) caused by anti-D, the safest options for transfusion are those that minimize the risk of additional immune reactions.

The correct choice indicates that either AB negative (which lacks A, B, and D antigens) or O negative blood (which also lacks A, B, and D antigens) is suitable since these blood types would not introduce any new antibodies that could react with the baby's existing anti-D antibodies. Furthermore, the selection of CMV-negative blood is crucial to reduce the risk of Cytomegalovirus transmission, particularly in vulnerable populations such as neonates. The requirement for irradiated blood also helps prevent transfusion-associated graft-versus-host disease, particularly in infants who may be more susceptible.

AB positive blood, while compatible in terms of ABO typing, carries D antigen which could provoke an immune response if the infant's HDN is due to anti-D, meaning that the infant has developed antibodies against the D antigen. Therefore, using AB positive or O positive blood could introduce a specific antigen against which the infant's immune system is reacting.

In summary, the optimal choice of transfusion for an AB-positive baby