Modulation of Human DCs by a Lactobacillus Strain Figure 7. Expression levels of TLR signalling pathway in DCs treated with L. paracasei, Salmonella or both. Comparison of the expression of NFKBIA, NFKB-1, TBK-1, IL-10 and TNF-a 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 fold change (Fc) represents the ratio of the expression in treated DCs to the expression in control cells. The data shown are the mean values and SEM of three independent experiments. *p,0.05 compared to controls; #p,0.05 compared to S.typhi. N.D indicate no detected. doi:10.1371/journal.pone.0043197.g007 of pro-inflammatory cytokines. Our data support the use of a supernatant similar to the one described in this paper as an effective and safe alternative instead of live bacteria. Our results contribute to the understanding of how probiotics exert their immunomodulatory effects. Materials and Methods Preparation of Bacteria and Probiotic Supernatant The probiotic strain (designated by the Pasteur Institute as L. paracasei CNCM I-4034) was isolated from the faeces of breast-fed newborn children. This strain was previously tested for antibiotic tolerance and resistance to gastrointestinal juices, bile salts, NaCl and low pH. The probiotic was grown in Man-Rogosa-Sharpe PLOS ONE | www.plosone.org 9 August 2012 | Volume 7 | Issue 8 | e43197