Meeting Abstract
Marsupials are a lineage of viviparous mammals that last shared a common ancestor with eutherians (placentals) over 148 million years ago. Marsupials are distinct from eutherians in that they give birth to highly altricial young after a short gestation. Whether or not there is regulation of maternal immune responses during marsupial pregnancy has been debated for decades. Indeed, the evolution of short gestation times has been attributed to a lack of immune regulation during marsupial pregnancy. Alternatively the maternal immune system may be entirely unaware of the presence of the fetal allograft in marsupials due to lack of a highly invasive placenta. To investigate this further, transcriptome analysis of uterine immune gene expression during pregnancy was performed in the gray short-tailed opossum, Monodelphis domestica. Gene expression profiles from pregnant and non-pregnant uterine tissues were generated using both NextGen sequencing and quantitative PCR. Analyses revealed expression of pro-inflammatory cytokines remained relatively low during pregnancy, even at implantation, but increased dramatically immediately preceding birth, peaking within twelve hours prior to parturition. These results contrast the two spikes of inflammation seen in eutherian pregnancy, first at implantation and second at parturition. Inflammation at terminal pregnancy in marsupials may be indicative of a parturition mechanism. Our results are consistent with the marsupial immune system being “aware” of the allogeneic fetus but under regulation.
