Lactobacillus Induced Heme Oxygenase 1 Figure 5. HO-1 expression is enhanced in Dendritic cells assocaited with JB-1. Dendritic cells were cultured from bone marrow and CD11c+ cells isolated and cocultured with PKH26 labeled L.rhamnosus JB-1 for 24 hr and HO-1 expression assessed by FACS. A) A dot plot showing a subpopulation of dendritic cells associated with the labeled lactobacillus. This is representative of 4 similar experiments. B) Representative dot plots and C) mean values of the percentage HO-1+ cells in the Lactobacillus associated (JB-1+ve) and non-associated (JB-1-ve) dendritic cell populations. Evidence for in vivo interaction between DC and JB-1 is provided by D) Representative dot plots and E) mean values of CFSE positive cells within the CD11c positive population from Peyers Patches of mice fed with CFSE labeled or unlabeled JB-1. Data presented as mean 6 SEM, n = 5, *p,0.05. CFSE = carboxyfluorescein diacetate succinimidyl ester. doi:10.1371/journal.pone.0047556.g005 live and killed JB-1 to induce HO-1 are warranted and may yield important information regarding mechanisms underlying the immunoregulatory actions of certain bacterial strains. The induction of HO-1 in DC appears to be another example of strain specific immunomodulation by commensal bacteria as the effect of JB-1 on DC was not mimicked by L.salivarius. Such strain specific effects are well established. Lyons et al [13] demonstrated differential induction of Foxp3+ T regulatory cells by three bacterial strains was associated with the ability to protect against allergic inflammation in mice. Maassen et al [45] analyzed eight different Lactobacillus strains and demonstrated marked differ- ences with respect to induction of pro-and anti-inflammatory cytokines in the gut mucosa. Similarly, Christensen et al. [46] showed that various lactobacillus species differentially stimulated mouse BMDC, with some strains strong inducers of IL-12 and TNF while others were weak inducers. It is still unclear exactly what underlies the distinct immunomodulatory effects of seemingly similar bacteria but small changes in only one microbe associated molecular pattern can result in significant changes in the immune response to bacteria. A study by Grangette et al [42] demonstrated PLOS ONE | www.plosone.org 7 October 2012 | Volume 7 | Issue 10 | e47556