Abstract

NanoFACS Isolated Placental Cell- and Size-Specific EVs and T-cell Polarization

Terry Morgan, Professor, Oregon Health and Science University

How the placenta suppresses the maternal immune response to this invasive fetal organ is a long-standing mystery. New data suggest that placental extracellular vesicles (EVs) isolated from first trimester placental explants in vitro induce immune tolerance (ie; Bai K et al, 2022).  This is similar to Treg induction by cancer EVs, but shares the method-based weakness of testing heterologous fractions of EVs from many different cell sources.  A significant advance would be to isolate placental cell- and size-specific EVs and culture them with T-cells to determine the dose-response effect. Moreover, an important negative control would be to test isolated liposomes from the same plasmas.  In this study, we hypothesize that placental invasive extravillous trophoblast EVs induce T-cell polarization from Th1 to Tregs compared with liposomes isolated from the same plasma samples.  We isolated placental EVs and spiked-in 200nm liposomes by nanoFACS from banked human first trimester plasma samples.  T-cell polarization cultures from banked PBMCs (positive control was IL-2 induced +/- TGF-b/retinoic acid) were validated and then compared with banked PBMCs treated with either placental EVs or liposomes. Our results show that placental EVs have PD-L1 on their surfac and compared with liposomes incubated with Th1 cells show significantly more Treg and Th2 polarization after 3 days in culture.