Maternal HLA-G*01:01:01:04 protects from anti-HLA-class II immunization in pregnant women

Factors determining anti-HLA immunization are poorly understood, although anti-HLA immunization following pregnancy is well described. The HLA-G molecule has been extensively described for its implication in immunological tolerance, especially during pregnancy. Transplant studies show an association between HLA-G haplotypes and alloimmunization. Our aim was to investigate the association of HLA-G haplotypes with anti-HLA class I and II immunization in a cohort of women having experienced one or more pregnancies and with no transfusion history. Maternal blood samples (n=270) collected at delivery and formerly screened for anti-HLA antibodies, HLA-A and HLA-B antigens, were screened by NGS for HLA-G gene polymorphism. Univariate analysis further confirmed that the number of pregnancies was significantly associated with anti-HLA class I immunization, whereas no other variable remained significant after Bonferroni correction. Our results showed however that anti-HLA class II immunization was associated with the number of children whereas the HLA-G*01:01:01:04 allele was protective against this immunization.