While the risk factors for alloimmunization are not fully understood, it is likely influenced by various immunological and genetic factors, according to a study recently published in Current Opinion in Immunology.
Alloimmunization can cause the mother to develop antibodies against fetal platelets during pregnancy and lead to fetal and neonatal alloimmune thrombocytopenia (FNAIT).
Currently, the International Society of Blood Transfusion has recognized 47 different human red blood cell blood group systems. These 47 different blood group systems encompass 362 different antigens. Among these 362 antigens, 184 are considered to be highly frequent, present in nearly 100% of individuals.
It is important for doctors to recognize the complex relationship between blood group systems and alloimmunization to ensure that blood transfusions do not trigger a response encompassing alloimmunization (given that foreign blood is imported into an individual). Furthermore, an appreciation of how blood group systems can trigger alloimmunization is important in the management of pregnancies complicated by this process.
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There are many studies that have shown a correlation between specific human leukocyte antigen (HLA) alleles and the development of alloimmunization targeted at the destruction of red blood cells. For example, HLA-DRB1*15 is known to increase the risk of D alloimmunization. Similar relationships can be shown in other forms of alloimmunization, such as anti-E, anti-Kell, anti-Fya, and anti-Jk(a).
Studies suggest that the inflammation status of a patient may play a role in alloimmunization. An example is sickle cell disease (SCD), a disease in which the shape of the red blood cells are distorted, causing them to lose some of their function. Patients with SCD have long-term inflammation; combined with genetic influence, these features may determine the risk of red blood cell alloimmunization.
For years, scientists have known that the fetus and the mother exchange cells during pregnancy, a process known as maternofetal microchimerism. This may set off a chain of biological reactions that modulate the process of alloimmunization.
“Although the risk factors for alloimmunization are still poorly understood, they appear to be multifactorial, involving immunological, genetic, and maternofetal microchimerism components,” the authors of the study wrote.
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