Page 1136 - Veterinary Immunology, 10th Edition

mammals (Chapter 31). Nevertheless, fetal allograft rejection does
VetBooks.ir not occur.

The initial steps in pregnancy include implantation of the
fertilized ovum in the uterine wall and its acceptance by the

mother's immune system. This implantation is regulated by
communication between the conceptus and the uterus. This
involves hormones such as progesterone and interferons, especially
IFN-τ and IFN-γ (Chapter 27).

In many species, pregnancy is associated with a strong skewing
of the mother's immune system in favor of Th2 responses and a
reduction in Th1 responses. (This raises the interesting concept that
infections that promote a strong Th1 response might reverse this

skewing, compromise pregnancy, and lead to abortion. This would
certainly apply to protozoan infections such as toxoplasmosis,
Neospora caninum infection, as well as brucellosis.)
The immunological destruction of the fetus and its trophoblast is

prevented by the combined activities of many different
immunoregulatory mechanisms acting at the maternal-fetal
interface (Fig. 34.8).

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