Which immunoglobulin is primarily responsible for hemolytic disease of the newborn?

Hemolytic disease of the newborn (HDN) primarily involves the immunoglobulin IgG. This condition occurs when there is an incompatibility between the blood types of the mother and the fetus, most commonly due to Rh factor differences. When a Rh-negative mother is carrying a Rh-positive baby, the mother's immune system may recognize the Rh-positive red blood cells as foreign and produce IgG antibodies against them.

IgG is capable of crossing the placenta, which is why it plays a crucial role in HDN. If the mother creates IgG antibodies against the fetal Rh-positive red blood cells, these antibodies can enter the fetal circulation and lead to destruction (hemolysis) of those cells. This process results in anemia, jaundice, and other complications for the newborn.

In contrast, IgA, IgM, and IgE are not involved in this specific scenario. IgA is primarily found in mucosal areas and secretions, playing a protective role at body surfaces. IgM is the first antibody produced in response to an infection or immunization and is unable to cross the placenta unlike IgG. IgE is mainly associated with allergic responses and parasitic infections, and does not typically play a role in HDN. Thus, Ig