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Figure 5. Extracellular vesicle-mediated feto-maternal immune tolerance. The feto-maternal immune tolerance that maintains normal pregnancy is partly mediated by BEVs from various microbiotas. Maternal BEVs can also carry DAMPs/PAMPs to the feto-maternal interface (placenta tissues) and trigger adverse immune responses that may manifest as feto-maternal allograft rejection in the form of graft-versus-host disease (GVHD). However, the threshold at which such a switch occurs, and the mechanisms involved are yet to be determined. Conversely, pathogenic bacteria can shed BEVs that can cause inflammatory responses often associated with adverse pregnancy conditions. BEV: bacterial extracellular vesicle; DAMPs/PAMPs: damage- and pathogen-associated molecular patterns; FM: feto-maternal; HEV: human extracellular vesicle. Created with BioRender.com.