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IgM is the first immunoglobulin expressed in the human fetus (around 20 weeks) [46] and phylogenetically the earliest antibody to develop. [47] IgM antibodies appear early in the course of an infection and usually reappear, to a lesser extent, after further exposure. IgM antibodies do not pass across the human placenta (only isotype IgG). [48]
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]
Anti-A and anti-B antibodies are usually IgM and do not pass through the placenta, but some mothers "naturally" have IgG anti-A or IgG anti-B antibodies, which can pass through the placenta. Exposure to A-antigens and B-antigens, which are both widespread in nature, usually leads to the production of IgM anti-A and IgM anti-B antibodies but ...
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.
The image above shows the interpretation of an antibody panel used in serology to detect antibodies towards the most relevant blood group antigens. Each row represents "reference" or "control" red blood cells of donors which have known antigen compositions and are ABO group O. The + symbol means that the antigen is present on the reference red ...
Anti-M and anti-N antibodies are naturally occurring, cold-reacting IgM-class antibodies. [7] Anti-M and anti-N are generally clinically insignificant. Anti-S, anti-s and anti-U antibodies are acquired following exposure (via pregnancy or past transfusion with blood products) and are warm-reacting IgG-class antibodies. [7]
Lewis antigens cannot be reliably detected until the 2nd birthday. Lewis antibodies in a pregnant woman are essentially totally insignificant because they are IgM subtype (don't cross the placenta) and Lewis antigen is weakly expressed during pregnancy (Lewis Le(a-b-) phenotype is commonly seen during gestation). [2]
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 .