Alloimmunization also known as isoimmunization, during pregnancy is the production of IgG antibodies by the mother against the paternally inherited antigens (IPA) in the foetus/newborn. The alloimmunization during pregnancy leads to various alloimmune disorders, such as, haemolytic disease of the foetus and newborn (HDFN), neonatal alloimmune neutropenia (NAN) and foetal and neonatal alloimmune thrombocytopenia (FNAIT) due to the production of maternal alloantibodies against the red blood cell antigen, neutrophils and platelets cell antigens, respectively. Recent studies suggest that maternal anti-HLA class I alloantibodies may also be the cause of FNAIT in addition to antibodies against platelet antigens. On the contrary, studies have also suggested that HLA-C, a classical HLA class I molecule, and HLA-G, a nonclassical HLA molecule, play an important role in placentation and modulation of the maternal immune system during pregnancy, respectively, and thereby leading to acceptance of the semi allogeneic fetus. So far most of the studies have discussed alloimmunization in pregnancy relating to Rh antigen. Thus, in this chapter an attempt has been made to discuss alloimmunization in pregnancy caused because of maternal alloantibody against HLA antigen and its role in immune modulation during pregnancy.
Part of the book: Complications of Pregnancy