Abstract
Human embryo implantation represents embryo apposition, adhesion to the endometrial
epithelium, and invasion into the stromal extracellular matrix within 1 to 2 days
during days 6 to 9 after ovulation. The major molecular mechanisms mediating implantation
include adhesion molecules, including mucins, selectins, integrins, and cadherins;
extracellular matrix components, such as laminins and collagens and their degrading
enzymes; phospholipids and immune regulatory molecules, including prostaglandins,
cytokines; and immunosuppressive molecules expressed by invasive trophoblasts and
endometrial cells. Many of these molecules are the targets for autoimmune reactions
in autoimmune diseases and cancer; however, the relevance of those in immune-mediated
implantation failure has not been defined. In this review, we will describe the molecules
involved in 2-day event of human embryo implantation, which may also be involved in
immune system activation and subsequently cause immune-mediated implantation failure.
We speculate that the data in the literature are limited concerning antiendometrial
antibodies because the endometrium might be taken as an immune-privileged site that
avoids autoimmune activation that might harm the implantation process. Antibodies
affecting human fertility in ways other than impairing implantation are outside the
scope of the current article and will not be discussed.
Keywords
adhesion molecules - autoantibodies - embryo implantation - endometrium - implantation
failure
