Effect of maternal anti-HPA-1a antibodies and polyclonal IVIG on the activation status of vascular endothelial cells

Abstract

Maternal anti-HPA-1a antibodies can cause severe fetal and neonatal alloimmune thrombocytopenia (FNAIT), complicated by intracranial haemorrhage (ICH). Antenatal treatment with maternal intravenous immunoglobulin (IVIG) seems to protect against ICH even when thrombocytopenia persists. The aim of this study was to investigate if anti-HPA-1a antibodies and IVIG potentially affect vascular endothelial cells (ECs) in order to identify susceptibility for ICH. Human umbilical cord endothelial cells (HUVEC) were incubated with anti-HPA-1a antibodies with or without polyclonal IVIG and evaluated for EC activation. Maternal sera with anti-HPA-1a antibodies affected neither the EC expression of intracellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1) and tissue factor (TF) nor the release of van Willebrand factor (vWF) or interleukin (IL)-8 nor the integrity of ECs. Maternal sera obtained after IVIG treatment and polyclonal IVIG decrease constitutive and cytokine-induced ICAM-1 and VCAM-1 expression on ECs. The results show that maternal anti-HPA-1a antibodies cause no activation or damage of ECs in this model. The clinical relevance of the de-activating properties of IVIG on EC activation with respect to ICH deserves further investigation.

Fig. 1

The effect of in vivo and of in vitro addition of IVIG on the expression of endothelial adhesion molecules. Secondary and tertiary monolayers of HUVEC were incubated for 24 h with incubation medium supplemented with 10% maternal sera either taken before (pre-IVIG serum), or after several weeks of IVIG treatment just prior to delivery (post-IVIG serum) and with 10% maternal pre-IVIG sera coincubated with polyclonal IVIG (preserum + IVIG). The cell cultures were analysed by flow cytometry for ICAM-1 and VCAM-1 surface expression. Values represent MFI (95% C.I) after logarithmic transformation of 16 experiments with ECs from different healthy newborns.

Fig. 2

Effect of IVIG on rHu-IFN-γ-induced expression of endothelial adhesion molecules. Secondary monolayers of HUVEC were incubated for 24 h with plain incubation medium (unstimulated ECs, representing constitutive endothelial ICAM-1 and VCAM-1 expression), or plain incubation medium supplemented with 50 U/ml rHu-IFN-γ, or with rHu-IFN-γ and polyclonal IVIG (IFN-γ+IVIG) or with polyclonal IVIG product (IVIG). The cells were analysed by flow cytometry for ICAM-1 and VCAM-1 expression. Values represent MFI of a representative experiment of three experiments with ECs from different healthy newborns.