Abstract
IntroductionMaternal alloimmunization against human platelet antigen (HPA)-1a has been implied to mediate both reduced birth weight and chronic placental inflammation. Fetal growth restriction is associated with different types of chronic inflammation in the placenta, mainly chronic histiocytic intervillositis and chronic villitis. The aim of this prospective study was to do a systematic examination of placentas from HPA-1a alloimmunized pregnancies, with focus on the histopathological and immunohistochemical diagnosis of variants of chronic inflammation. Material and methodsIn a Polish-Norwegian study, 48 placentas were examined. The histopathology of placentas from 27 HPA-1a immunized women was compared with 21 placentas from non-immunized HPA-1a negative women (controls). In the group of alloimmunized women, ten received antenatal intravenous immunoglobulin G (IVIg). Tissue sections from formalin fixed paraffin embedded placental tissue were stained with hematoxylin and eosin and microscopically examined with focus on various types of chronic placental inflammations. ResultsChronic histiocytic intervillositis was observed in 40.7% of placentas from HPA-1a alloimmunized pregnancies, compared to none in the control group (p = 0.001). Chronic villitis of unknown etiology was more frequently found in the alloimmunized group, however this difference was not statistically significant. Maternal administration of IVIg did not seem to protect against chronic inflammatory lesions. DiscussionPlacentas with detectable maternal anti-HPA-1a antibodies are associated with highly increased risk of low-grade chronic histiocytic intervillositis.
Highlights
Maternal alloimmunization against human platelet antigen (HPA)-1a has been implied to mediate both reduced birth weight and chronic placental inflammation
Norwegian placental biopsies were added to the PREVFNAIT biobank in 2015 for the purpose of this study and the current study was approved by the Regional Committee for Medical Research Ethics, North Norway (REK Nord 2015/2192)
We found a strong association between anti-platelet antibodies towards the HPA-1a antigen in maternal plasma and chronic histiocytic intervillositis in the placenta
Summary
Maternal alloimmunization against human platelet antigen (HPA)-1a has been implied to mediate both reduced birth weight and chronic placental inflammation. Fetal growth restriction is associated with different types of chronic inflammation in the placenta, mainly chronic histiocytic intervillositis and chronic villitis. The aim of this prospective study was to do a systematic examination of placentas from HPA-1a alloimmunized pregnancies, with focus on the histopathological and immunohistochemical diagnosis of vari ants of chronic inflammation. Discussion: Placentas with detectable maternal anti-HPA-1a antibodies are associated with highly increased risk of low-grade chronic histiocytic intervillositis. The most serious complication is Abbreviations: FNAIT, Fetal and neonatal alloimmune thrombocytopenia; HPA, Human platelet antigen; ICH, Intracranial hemorrhage; IVIg, Intravenous immunoglobulin G. intracranial hemorrhage (ICH) [3]. An antibody-mediated prophy laxis to prevent HPA-1a alloimmunization is currently in clinical trials [10]
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