Molecular analysis of human HLA-G+ trophoblasts reveals their strong immune regulatory potential (P2172)

Abstract INTRODUCTION: During pregnancy HLA-G+ extravillous trophoblasts (EVTs) play a key role in the prevention of a maternal immune attack to allogeneic fetal tissue. Human EVTs are extremely difficult to study due to their low frequency and lack of proliferative capacity. In this study we obtained robust villous trophoblast (VT) and EVT preparations and performed microarray analysis on RNA isolates. RESULTS: Comparison of the expression profiles revealed >4000 differentially expressed genes based on a 2-fold difference. To identify functional differences a Gene Set Enrichment Analysis (GSEA) was performed. In EVTs, 14 functional gene sets out of the 20 most significantly enriched gene sets were associated with direct immune activation. The core genes of these immune pathways include cytokines (e.g. EBi3, TGFβ and IL8) and cell surface molecules (e.g. B7-H3 and CRTAM) which can all directly influence lymphocyte binding and activation. To evaluate the implications of this immune activating profile, co-cultures of EVT with decidual NK (dNK) cells and decidual T (dT) cells were established. Low percentages of dNK and dT cells form immune synapses with HLA-G+ EVTs. Preliminary analysis of dNK-EVT and dT-EVT co-cultures demonstrates that EVTs influence the expression of activation markers on decidual lymphocytes. CONCLUSION: Our data supports the hypothesis that proper immune activation, rather than general immune suppression, facilitates the establishment of fetal-maternal tolerance.