Differential expressions of toll-like receptor genes in the vagina of pregnant mice.

The mammalian immune system is classified into two categories, innate and adaptive immunity, and innate immunity is an immunological first line of defense for the mucosal immune system. Toll-like receptors (TLRs) play critical roles in innate immunity, as they recognize specific molecular patterns found in microbial pathogens, and the activation of TLRs is an important step not only for the innate immune response, but also for the development of the subsequent antigen-specific adaptive immune response. Despite the importance of TLRs in mucosal immunity, little is known about their expression in the female genital mucosa during gestation. In the present study, gene expressions of TLRs 1 to 9 were investigated together with NF-κB and FoxP3 gene expressions in the vaginae of pregnant mice to understand the immune response of the female genital mucosa during pregnancy. We found that mRNA expressions of TLR4, TLR5, TLR6, TLR7 and TLR9 were significantly decreased during the late gestation period, whereas temporary increases were seen in the middle gestation period. Gene transcriptions of TLR1, TLR2, TLR3 and TLR8 were not changed specifically during the gestation period. The mRNA expression of NF-κB was not changed at any time during the gestation period, while the FoxP3 mRNA expression was increased in the middle gestation period. These results suggest that expressions of particular TLRs would be down-regulated during gestation so as to maintain the pregnant state.