Role of T-cell cytokines in decidua and in cumulus oophorus during pregnancy.

We focus on the roles of decidual and cumulus oophorus T cells. It was suggested that Th1-type cytokines (IFN-gamma and TNF-beta), which promote allograft rejection, may compromise pregnancy, whereas the Th2-type cytokines (IL-4, IL-5, IL-10) inhibiting the Th1 responses promote allograft tolerance and therefore may improve fetal survival. We found that T cells' leukemia inhibitory factor (LIF), M-CSF, IL-4 and IL-10 production at the fetomaternal interface could contribute to the maintenance of pregnancy. Interestingly, we did not find an increased production of IFN-gamma by decidual T cells during spontaneous abortion, as expected. We detected T cells in the cumulus oophorus, which surrounds the oocyte during ovulation and the egg before implantation. Cumulus oophorus T cells produce higher levels of IL-4 and LIF than the T cells of peripheral blood or the ovary. We can only speculate what the factors present in the microenvironment of the T cells are that could be responsible for the cytokine profile of decidual and cumulus oophorus T cells. Hormones present in the decidua and in the cumulus oophorus could be the first candidates. In particular, progesterone is a potent inducer of production of Th2-type cytokines, LIF and M-CSF. Other candidates could be molecules produced by the trophoblast or the embryo.