Maternal human leukocyte antigen (HLA) antibodies may contribute to fetal and neonatal alloimmune thrombocytopeniaFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth. (FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth.), particularly when antibody levels are high, according to a study recently published in Vox Sanguinis: International Journal of Transfusion Medicine.
While FNAIT is most commonly linked to maternal antibodies against human platelet antigenHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT.-1a (HPAHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT.-1a), whether HLA antibodies also play a role has remained uncertain.
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To investigate this question, researchers analyzed maternal and neonatal samples from 80 pregnancies referred to Australian Red Cross Lifeblood for FNAIT testing between July 2018 and June 2022. They then compared these findings with samples from 150 healthy pregnancies in which infants had normal platelet counts at birth.
The researchers found no significant differences between the FNAIT and control groups in maternal age, parity or number of pregnancies. As expected, newborn platelet counts were substantially lower in the FNAIT group. One in five FNAIT cases had a previous history of the condition, while thrombocytopeniaThrombocytopenia A platelet count that is lower than normal. was the primary reason for referral in 82% of cases.
All participants underwent comprehensive testing for platelet antigen incompatibility and antibodies, while HLA antibody screening and typing were performed using Luminex- and PCR-based methods.
Although HLA antibodies were detected in both groups, their strength differed significantly, with mothers in the FNAIT group having markedly higher HLA antibody mean fluorescence intensity (MFI) values compared to the control group.
Among the different antibody types, HLA-A and HLA-B antibodies demonstrated significantly higher MFI values than HLA-C antibodies.
“Though the Luminex assay is only semi quantitative, HLA antibodies were detected in the control group (all the neonates had normal platelet counts) at significantly lower MFI levels compared to FNAIT cases and may indicate a role for HLA antibodies in FNAIT if present at higher MFI levels,” the researchers concluded.
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