earticle

영어

For the establishment of successful pregnancy the maternal immune system must tolerate the implanting semi-allogenic conceptus, but the mechanism underlying this process is not fully understood in pigs. Among many factors, members of the tumor necrosis factor superfamily (TNFSF) have been considered as important immune regulators in cell-mediated immunity. TNFSF members bind to their responsive receptor containing cytoplasmic death domain to induce apoptosis in immune cells. Action of TNFSF members at the during pregnancy has been studied in some species including humans, mice and cows, suggesting that the TNFSF-induced apoptosis of activated maternal immune cells at the maternal-conceptus interface may be one of the mechanisms against rejection of semi-allogenic fetus. However, the expression and function of TNFSF members at the maternal-conceptus interface have not fully understood in pigs. Thus, to initiate the study on the role of TNFSF members for the establishment of pregnancy, we determined the expression of the TNFSF members, CD40 ligand (CD40LG), FAS ligand (FASLG), TNFα and TNF-related apoptosis inducing ligand (TRAIL; TNFSF10) in the endometrium and conceptus tissues during pregnancy in pigs. Real-time RT-PCR analysis showed that CD40LG, FASLG, TNFα and TNFSF10 mRNAs were expressed in the uterine endometrium during the estrous cycle and pregnancy. Levels of CD40LG, FASLG, TNF-α and TNFSF10 mRNA in endometrial tissues significantly increased on Day 15 of pregnancy, and levels of FASLG, TNF-α and TNFSF10 were also high on Day 60 of pregnancy and decreased thereafter. Immunohistochemical analysis showed that CD40LG and TNFSF10 proteins were localized mainly to luminal epithelial (LE) cells on Day 15 of pregnancy and amniotic membrane during late pregnancy, while FASLG protein was localized to LE cells during Day 30 to term and glandular epithelial cells during the estrous cycle and pregnancy. To understand the regulatory mechanism of endometrial CD40LG, FASLG and TNFSF10 expression by conceptus-derived cytokines, we treated endometrial tissues with increasing doses of interferon-γ (IFNG) and interferon-δ (IFND) and found that IFNG increased the expression of CD40L, TNFα and TNFSF10 mRNA, but not FASLG mRNA, and IFND increased TNFSF10 mRNA. To further understand the role of TNFSF10 on apoptosis of immune cells at the maternal-conceptus interface, we measured cell death of peripheral blood mononuclear cells by uterine epithelial cells expressing TNFSF10, and found that TNFSF10-expressing epithelial cells decreased survival of immune cells, especially of myeloid lineage. These results showed that CD40LG, FASLG, TNFα and TNFSF10 were expressed in a cell-type and stage-specific fashion in the endometrium during pregnancy, suggesting that CD40LG, FASLG, TNF and TNFSF10 may play an important role in the establishment of pregnancy by regulating the maternal immune response at the maternal-conceptus interface in pigs.