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View submission: Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology
How is the placenta ensuring that a fetus is not harmed by the mothers immune system? there should be incompatibilities in the expressed MHC? I also remember that certain antibodies can cross the "blood-placenta-border" (unsure if that's the correct term) but others can't, but it doesn't form a cohesive picture for me yet.
Comment by CrateDane at 12/03/2025 at 18:43 UTC
6 upvotes, 1 direct replies
The placental cells do not express the typical MHC I types HLA-A and HLA-B, but instead express HLA-E and HLA-G. The absence of HLA-A and HLA-B helps prevent recognition as non-self and attack by cytotoxic T cells, while the expression of HLA-E and HLA-G helps show self and avoid attack by natural killer cells.
But that's just one aspect. The physical barrier is another important part. The placenta also secretes immunosuppressant molecules, and so on. It's a complicated topic.
It also sometimes fails, leading to things like pre-eclampsia or rhesus disease.