antid

anti-D refers to an alloantibody directed against the D antigen of the Rh blood group system. It is typically an IgG antibody produced by Rh(D)-negative individuals after exposure to D antigen, most often through transfusion of D-positive blood or during pregnancy when the fetus is D-positive. Anti-D is one of the most clinically significant Rh antibodies because of its potential to cause hemolysis of D-positive red cells and, in pregnancy, hemolytic disease of the fetus and newborn (HDN).

In transfusion medicine, anti-D can trigger hemolytic reactions if a recipient lacking the D antigen receives D-positive red cells. In pregnancy, maternal anti-D antibodies can cross the placenta and bind fetal D-positive red cells, leading to fetal anemia and, in severe cases, hydrops fetalis. The risk to the fetus depends on antibody titer, specificity, and the timing of exposure.

Detection and monitoring rely on serologic testing. An indirect antiglobulin test (IAT) is used in antibody screens to identify anti-D in the recipient’s plasma. A direct antiglobulin test (DAT) on newborn red cells can indicate HDN due to anti-D. Antibody identification helps distinguish anti-D from other clinically significant Rh antibodies and guides management.

Prevention and management include Rh immune globulin (RhIG) prophylaxis for Rh-negative pregnant women during pregnancy and after delivery to prevent anti-D formation following exposure to D antigen. In transfusion practice, careful matching for D antigen and ongoing monitoring help reduce risks associated with anti-D.