n the present study, the increase in COX-2 expression after treatment with IFN-т was observed only in the ipsi horn of the uterus. The same side-specific effect was reported when studying the regulation of the EP2 receptor. On the other hand, there is no similar difference in the regulation of GM-CSF, and IFN receptors are expressed uniformly in the ipsi and the contralateral horns. Because the antiluteolytic effects of IFN-т are P4 dependent, and because P4 stimulates endometrial synthesis of PGs and is more concentrated in the ipsi horn, it is possible that the effect of IFN-т on the PG axis is favored in the ipsi horn.
During pregnancy, PGE2 concentrations are more elevated in the ipsi horn, and this may reflect both the contribution of the conceptus and the up-regulation of COX-2 in the maternal epithelium. It is well known that COX-2 is an important regulator of the implantation process and that attachment begins in the ipsi horn before spreading to the contralateral horn. Moreover, embryos transferred in the ipsi horn have greater chances of survival, whereas embryos deposited in the contralateral horn have a tendency for transuterine migration.
Pregnancy recognition in ruminants occurs when IFN-т from the trophoblast prevents the increase of OTRs in the LE, thus disrupting luteolytic pulses of PGF2a.