Which condition would result in HDN?

Which condition would result in HDN?

• A. Exposure to antigen found on both mother and baby RBCs
• B. Prior exposure to foreign RBC antigen
• C. Buildup of IgE on mother's cells
• D. Sensitization of cytotoxic T cells

Answer: (B)

Hemolytic disease of the newborn happens when the mother makes IgG antibodies against a fetal red blood cell antigen that she does not have herself. Those antibodies can cross the placenta and bind to the baby's RBCs, marking them for destruction by the fetal reticuloendothelial system. This immune reaction is most common when there has been prior exposure to a foreign RBC antigen—such as from a previous pregnancy or a transfusion—so the mother becomes sensitized. In a subsequent pregnancy with fetal cells carrying that antigen, the maternal antibodies attack the newborn’s RBCs, causing hemolysis and anemia. If the antigen is shared between mother and fetus, there’s no mismatch to provoke antibody production, so HDN is unlikely. IgE involvement points to allergic-type responses rather than the IgG-mediated mechanism in HDN. Sensitization of cytotoxic T cells would imply a cell-mediated attack, not the antibody-mediated destruction of red cells seen in HDN.

Hemolytic disease of the newborn happens when the mother makes IgG antibodies against a fetal red blood cell antigen that she does not have herself. Those antibodies can cross the placenta and bind to the baby's RBCs, marking them for destruction by the fetal reticuloendothelial system. This immune reaction is most common when there has been prior exposure to a foreign RBC antigen—such as from a previous pregnancy or a transfusion—so the mother becomes sensitized. In a subsequent pregnancy with fetal cells carrying that antigen, the maternal antibodies attack the newborn’s RBCs, causing hemolysis and anemia.

If the antigen is shared between mother and fetus, there’s no mismatch to provoke antibody production, so HDN is unlikely. IgE involvement points to allergic-type responses rather than the IgG-mediated mechanism in HDN. Sensitization of cytotoxic T cells would imply a cell-mediated attack, not the antibody-mediated destruction of red cells seen in HDN.