Signal transduction induced by Lactobacillus spp. (A) HEK293T cells were transiently transfected with 0.5 μg of each of pcDNA3.1(+)-mCD14, pGL3-NF-kB-luc, and pRL-SV40 (as an internal control), plus 0.5 μg of one of the following: pcDNA3.1(+) (EV), pEFBOS-mTLR2/Flag (TLR2), or p3XFlag-mTLR4 (TLR4). At 48 h after the transfection, the cells were untreated, treated with LTA (1 μg/ml) of L. fermentum (F) or L. casei (C) or with synthetic lipid A (1 μg/ml) (A) for 8 h, and then lysed to measure the luciferase activities. The experiment was repeated three times, yielding similar results, and a typical result is shown. (B) HEK293T cells were transiently transfected with 0.5 μg each of pcDNA3.1(+)-mCD14, pGL3-NF-kB-luc, and pRL-SV40, plus 1 μg of one of the following: pcDNA3.1(+) (EV), pEFBOS-mTLR2/Flag (TLR2) plus pcDNA3/1(+) (0.5 μg each), or the combination of pEFBOAS-mTLR2/Flag and pEFBOS-mTLR6/Flag (0.5 μg/each) (TLR2 + TLR6). At 48 h after the transfection, the cells were either not treated or treated with heat-killed L. fermentum (1 μg/ml) for 8 h and then lysed for the measurement of the luciferase activities. The experiment was repeated three times, yielding similar results, and a typical result is shown. (C) Lactobacillus LTA induces JNK activation in RAW264.7 cells. RAW264.7 cells were either not treated or treated with 1 μg of either LPS or purified LTA from L. fermentum/ml for 30 min. Cells were lysed, and the JNK1 kinase activity was measured by using GST-c-Jun as the substrate.