In article <3fh9ie$3kb at agate.berkeley.edu>,
frauwirt at notmendel.Berkeley.EDU (Ken Frauwirth (BioKen)) wrote:
> In article <1995Jan17.153755.9166 at newsserver.rrzn.uni-hannover.de>,
> <nhchpelt at rrzn-user.uni-hannover.de> wrote:
> >Why is an embryo not regarded as foreign tissue to a pregnant mother?
> >Why does the maternal immune system tolerate it?
> >Doesn't the embryonic tissue express any antigens/MHCs which could stimulate
> >the mother's immune answer?
> I believe that this is mainly due to the fact that the mother's cellular
> immune system has no access to the baby (and much of the immune response
> relies on cell-cell interactions). Thus, the only interactions can be with
> soluble antigens, which should not differ significantly from mother to baby.
> One big exception is the Rh factor. If the mother is Rh- and a baby is Rh+,
> then a primary antibody response is generated. However, IgM (the main
> antibody type in a primary response) cannot cross the placenta, so the child
> is safe. If a second Rh+ baby is produced, however, a secondary response is
> elicited. Since IgG (the main antibody in a secondary response) *can* cross
> the plancenta, this can cause "rejection" of the fetus, resulting in a
> miscarriage.
All well, but if I am not mistaken one has to view the embryo as
"non-self" and the only reason the embryo isn't gobbeled up by the
mother's immune defence is the mother-embryo barrier?
Frode
