Pregnancy represents a paradox, since the foetus which expresses both maternal and paternal antigens, is tolerated by the maternal immune system. The immune system which normally recognizes and launches immune responses towards antigens not recognized as self does not during normal pregnancy attack the paternal antigens expressed by the foetus. The foetus is not only tolerated but it is also allowed to grow and even develop its own immune system.

Although it is not fully understood how this tolerance is obtained and sustained, it is known that both systemic and local changes in the mother immune system occurs. Locally in the decidua, the uterine lining during pregnancy, the cell composition differs from that found in blood. Macrophages and NK cells are the major cell types in the decidua.

These macrophages, which are alternatively activated, and trophoblasts, placental cells of foetal origin, are believed to be involved in foetal tolerance.       

The aim of this study was to first develop a migration assay and then test the recruitment ability of macrophages and trophoblasts.