Gf. Clark et al., A ROLE FOR GLYCOCONJUGATES IN HUMAN-DEVELOPMENT - THE HUMAN FETO-EMBRYONIC DEFENSE SYSTEM HYPOTHESIS, Human reproduction, 11(3), 1996, pp. 467-473
The mechanisms underlying the protection of the human embryo/fetus fro
m the maternal immune response are poorly understood. Substantial evid
ence indicates that carbohydrate recognition plays a primary role in t
he sequestration of leukocytes during inflammatory processes, lymphocy
te homing, and initial gamete binding. Our previous studies suggest a
possible convergence in the types of carbohydrate sequences recognized
during initial human gamete binding and immune/inflammatory cell inte
ractions. Our more recent findings indicate that oligosaccharides part
icipating in such processes are also associated with soluble glycoconj
ugates found in the human placenta, amniotic fluid, and decidua. We th
eorize that such glycoconjugates may abrogate the maternal immune/infl
ammatory response by blocking the primary adhesive interactions requir
ed for the expression of such activities. Foreign embryonic cells may
also be protected by surface expression of oligosaccharide sequences t
hat suppress immune effector cell action in a manner not dependent upo
n classical major histocompatibility (MHC) recognition. Glycoconjugate
s expressing selectin ligands may also manifest a potent contraceptive
effect that may also be beneficial for both the mother and the develo
ping embryo/fetus. This hypothesis provides a preliminary framework fo
r understanding how temporally and spatially restricted immunosuppress
ive effects could be expressed in utero that protect the human embryo/
fetus during this period of human development.