Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is caused by a dysfunctional maternal immune response that causes the mother’s immune system to mistakenly attack fetal blood cells, causing harm to the fetus.
Read on to understand more about how and why FNAIT occurs.
Recognition of foreign antigens
Platelets are a type of red blood cells that are produced in response to bleeding. For example, if you accidentally cut yourself, platelets are activated to stem the bleeding. Without adequate platelet levels, bleeding may continue for much longer, resulting in a significant loss of blood.
Read more about FNAIT causes and risk factors
Platelets express antigens, which are like cell signatures. FNAIT occurs when the fetus inherits platelet antigens from the father that the mother does not share. As a result, the mother’s immune system may recognize these antigens as foreign. The immune system is adapted to attack foreign antigens, which is how it fights against foreign substances such as infections.
Production of antibodies
When the maternal immune system recognizes fetal platelet antigens as foreign, it develops antibodies to destroy them. This is a dysfunction of the maternal immune system, as this is not supposed to happen during pregnancies. When the mother develops these antibodies, they are trained to attack the platelet antigens they recognize as foreign, destroying the platelets.
Placental Transfer
These maternal antibodies reach the fetus by crossing the placenta and entering the fetal blood circulation. Once these antibodies identify fetal platelet antigens, they will begin attacking them. This process causes the fetal platelet count to fall, meaning that the fetus is unable to produce enough platelets, should internal bleeding occur.
After birth, the newborn will still have a low platelet count as a result of maternal antibody destruction during pregnancy. As such, an infant affected by FNAIT needs to be closely monitored to prevent internal bleeding episodes, which can be life-threatening, especially if bleeding occurs in the brain.
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