An Rh antibody is an antibody produced by an Rh-negative individual in response to exposure to Rh-positive red blood cells.
Understanding Rh Factor and Antibodies
Rh factor, also known as the Rhesus factor, is a protein found on the surface of red blood cells. People who have this protein are Rh-positive, while those who lack it are Rh-negative. Problems can arise when an Rh-negative individual is exposed to Rh-positive blood, typically during pregnancy or blood transfusions.
How Rh Antibodies Develop
When an Rh-negative person is exposed to Rh-positive blood, their immune system recognizes the Rh factor as foreign. This triggers the production of Rh antibodies, specifically designed to target and destroy Rh-positive red blood cells. This process is called Rh sensitization.
The Impact of Rh Antibodies
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Pregnancy: The most significant concern is during pregnancy. If an Rh-negative mother is carrying an Rh-positive fetus, fetal red blood cells can cross the placenta and enter the mother's bloodstream, particularly during delivery. The mother's immune system can then produce Rh antibodies. These antibodies can cross the placenta in subsequent pregnancies and attack the red blood cells of an Rh-positive fetus, leading to hemolytic disease of the fetus and newborn (HDFN).
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Blood Transfusions: Rh antibodies can also cause problems during blood transfusions. If an Rh-negative person who has Rh antibodies receives Rh-positive blood, the antibodies will attack the transfused red blood cells, causing a potentially severe transfusion reaction.
Prevention with Rh Immunoglobulin (RhIg)
Fortunately, HDFN is largely preventable with Rh immunoglobulin (RhIg). RhIg, also known as RhoGAM, is a medication containing Rh antibodies. When given to an Rh-negative pregnant woman who may be carrying an Rh-positive fetus, RhIg prevents her immune system from recognizing the fetal red blood cells and producing her own, more harmful Rh antibodies. RhIg works by binding to any fetal Rh-positive red blood cells in the mother's circulation and removing them before her immune system can react.
Detecting Rh Antibodies
Rh antibodies can be detected through a blood test called an antibody screen or indirect Coombs test. This test is typically performed during pregnancy to determine if an Rh-negative woman has developed antibodies against Rh-positive red blood cells.
