Modulation of Human DCs by a Lactobacillus Strain Figure 4. Expression of TLRs genes in DCs in the presence of L. paracasei, Salmonella or both. Comparison of the expression of TLR1, TLR2, TLR3, TLR4 and TLR5 in DCs in the presence of the probiotic (Prob), its supernatant (CFS), Salmonella (S.typhi) or a combination. LPS, 20 ng/ml, was used as a positive control. The data shown are the mean values and SEM of three independent experiments. The fold change (Fc) represents the ratio of the expression in treated DCs to the expression in control cells. *p,0.05 compared to controls; #p,0.05 compared to S.typhi. N.D indicate no detected. doi:10.1371/journal.pone.0043197.g004 of the changes in gene expression patterns in probiotic-treated human DCs [35]. Our results showed that L. paracasei CNCM I- 4034 and its CFS stimulated TLR9 expression in the presence or absence of enterobacteria. Similarly, several studies have described increased expression of TLR9 upon the administration of probiotics, such as L. johnsonii and L. casei [36,37]. Recently, it has been proposed that apical TLR9 stimulation in intestinal epithelial cells leads to a heightened state of immune surveillance [37]. These results indicate that this TLR is crucial for the regulation of pro-inflammatory cytokines, which is consistent with a recent study that correlated the presence of this TLR with the anti-inflammatory effect induced by probiotics [35]. Moreover, as expected, our probiotic strain activated the expression of TLR2. PLOS ONE | www.plosone.org 6 August 2012 | Volume 7 | Issue 8 | e43197