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Immunoglobulin M (IgM) is the largest of several isotypes of antibodies (also known as immunoglobulin) that are produced by vertebrates. IgM is the first antibody to appear in the response to initial exposure to an antigen ; [ 1 ] [ 2 ] causing it to also be called an acute phase antibody.
Routine antenatal antibody screening blood tests (indirect Coombs test) do not screen for ABO HDN. [citation needed] If IgG anti-A or IgG anti-B antibodies are found in the pregnant woman's blood, they are not reported with the test results, because they do not correlate well with ABO HDN.
The immune response to A and B antigens, which are widespread in the environment, usually leads to the production of IgM or IgG anti-A and anti-B antibodies early in life. Women of blood type O are more prone than women of types A and B to making IgG anti-A and anti-B antibodies, and these IgG antibodies are able to cross the placenta.
Immune tolerance in pregnancy or maternal immune tolerance is the immune tolerance shown towards the fetus and placenta during pregnancy. This tolerance counters the immune response that would normally result in the rejection of something foreign in the body, as can happen in cases of spontaneous abortion .
Hemolytic disease of the fetus and newborn (HDN) is a condition where the passage of maternal antibodies results in the hemolysis of fetal/neonatal red cells. The antibodies can be naturally occurring such as anti-A, and anti-B, or immune antibodies developed following a sensitizing event. [ 12 ]
Mothers who are negative for the Kell 1 antigen develop antibodies after being exposed to red blood cells that are positive for Kell 1.Over half of the cases of hemolytic disease of the newborn owing the anti-Kell antibodies are caused by multiple blood transfusions, with the remainder due to a previous pregnancy with a Kell 1 positive baby.
Since these antibodies sometimes destroy red blood cells they can cause anemia; this test can help clarify the condition. The indirect Coombs test detects antibodies that are floating freely in the blood. [1] These antibodies could act against certain red blood cells; the test can be carried out to diagnose reactions to a blood transfusion. [1]
Blood compatibility testing is routinely performed before a blood transfusion.The full compatibility testing process involves ABO and RhD (Rh factor) typing; screening for antibodies against other blood group systems; and crossmatching, which involves testing the recipient's blood plasma against the donor's red blood cells as a final check for incompatibility.