Which type of antibodies are classified as Rh antibodies?

Rh antibodies, specifically those related to the Rh blood group system, are primarily classified as IgG antibodies. This classification is significant because IgG antibodies are the most abundant type of antibody found in blood circulation and are known for their ability to cross the placenta. In the context of Rh incompatibility, when an Rh-negative individual is exposed to Rh-positive blood (for example, during pregnancy with an Rh-positive fetus), the immune system can produce IgG antibodies against the Rh factor. These antibodies can cross the placenta and affect the fetus in conditions like hemolytic disease of the newborn (HDN).

While other antibody classes exist, such as IgA, IgM, and IgD, they have distinct roles and characteristics. IgM is typically the first antibody produced in response to an infection but does not cross the placenta; IgA is commonly found in mucosal areas and secretions but is not involved in the Rh system; IgD primarily functions as a receptor on B cells and is not significant in the context of Rh antibodies. Therefore, the identification of Rh antibodies as IgG is critical in understanding blood group immunology and the implications for pregnancy and transfusion medicine.