TLR9 is a member of the toll-like receptor (TLR) family which plays a fundamental role in pathogen recognition and activation of innate immunity. TLRs are named for the high degree of conservation in structure and function seen between mammalian TLRs and the Drosophila transmembrane protein Toll. TLRs are transmembrane proteins, expressed on the cell surface and the endocytic compartment and recognize pathogen-associated molecular patterns (PAMPs) that are expressed on infectious agents and initiate signalling to induce production of cytokines necessary for the innate immunity and subsequent adaptive immunity. The various TLRs exhibit different patterns of expression. This gene is preferentially expressed in immune cell rich tissues, such as spleen, lymph node, bone marrow and peripheral blood leukocytes. Studies in mice and human indicate that this receptor mediates cellular response to unmethylated CpG dinucleotides in bacterial DNA to mount an innate immune response. Placental alkaline phosphatase is one of the most stable isoenzyme, only existing in the placenta of higher primates. These characteristics make placental alkaline phosphatase suitable to use as a reporter gene for the analysis of promoter activity and gene expression in cell culture and animal serum. The natural form of placental alkaline phosphatase (PLAP) is membrane anchored. The recombinant form of placental alkaline phosphatase (secreted alkaline phosphatase, SEAP) is used for reporter gene function. SEAP is created by inserting a translational terminator after amino acid 489 (Berger, et al., Gene 66 : 10. This mutation converts the membrane-bound PLAP protein into the secreted protein. As a major transcription factor, NF-kB plays a key role in regulating genes responsible for the innate and adaptive immune responses. In unstimulated cells, the NF-kB dimers are held in the cytoplasm by IkBs that masks the nuclear localization signals of NF-kB. Upon cell stimulation, which leads to IkB degradation, NF-kB quickly translocates to the nucleus and activates various genes that have DNA-binding sites for NF-kB.