Problem: The placenta is a highly selective barrier against the hematogenous dissemination of infectious agents. Despite the presence of seemingly intact physical and immunologic barriers, infections nonetheless occur. These observations prompted the examination of placental tissue, amnion, and chorion for previously unrecognized protective mechanisms.
Method of study: Messenger RNA from term placenta, amnion, and chorion were reverse transcribed using a 3' RACE adapter. 3' rapid amplification of cDNA ends (RACE)-polymerase chain reaction (PCR) was conducted on cDNA from these tissues to detect the presence of human defensins. Southern analysis and partial sequence analysis were subsequently performed to confirm identity.
Results: PCR amplification of placental, amnion, and chorion cDNA yielded a 468-bp product and a weakly detectable band of 300 bp. Southern analysis demonstrated two corresponding hybridizing bands in the placenta, amnion, and chorion but not from a negative cDNA control. Partial sequence analysis of the 468-bp product from placenta confirmed the presence of either defensin 1 or 3 in human placenta.
Conclusions: The human placenta, amnion, and chorion express defensins at the level of transcription. These findings suggest that a novel and previously unrecognized mechanism of protecting the fetus against infection may be present within these tissues.