Dition of immunosuppressive agents,pharmacological modulation, or inhibitory cytokines when DCs are being generated from monocytes influences the functional properties of the resulting DCs [9,10]. Several agents, including glucocorticoids [25] such as dexamethasone [26,27], mycophenolic acid [28], vitamin D3 (1a,25-dyhydroxyvitamin D3) [29], retinoic acid [30], the combination of dexamethasone and vitamin D3 [31], or IL-10 [32] have been used to render DCs resistant to maturation [33]. Tolerogenic DCs have been shown to induce T-cell anergy [34], suppress effector T cells, and promote 25033180 the generation of regulatory T cells (Tregs) [14,35]. Interestingly, some studies [14] have reported that the maturation of dex-conditioned DCs with LPS potentiates the tolerogenic phenotype of DCs. We performed a detailed phenotype analysis in order to compare iDCs and fully mature DCs with tol-DCs from healthy donors and patients with Crohn’s disease and address the stability of tol-DCs. DCs conditioned with dexamethasone displayed a semi-mature phenotype, which is consistent with the tolerogenic DC phenotypes described elsewhere [36]. We also observed an alteration in the DC maturation process; characterized by low-Tolerogenic Dendritic Cells Response to BacteriaFigure 4. Tol-DCs possess a stable phenotype. DCs were carefully washed to eliminate cytokines and dexamethasone, and viable DCs were further re-challenged with 100 ng/ml of LPS or 1 mg/ml of soluble CD40L as second stimuli. After 24 h, the phenotype (A) was analyzed by flow cytometry. Data 14636-12-5 web represent relative MFI increase induced by LPS (n = 6) or CD40L (n = 4) compared to unstimulated iDCs, mDCs or tol-DCs as control. (B) IL-10 concentration is shown in pg/ml. IL-12p70 and IL-23 were not detected (detection limit = 7.8 pg/ml). Student’s t-test: *p,0.05, **p,0.001. (C) Tol-DCs do not recover the ability to stimulate T cells after re-challenge. T-cell proliferation was determined in triplicate by 3H-thymidine incorporation. IFN-c and IL-10 production in the supernatant was analyzed. doi:10.1371/journal.pone.0052456.gTolerogenic Dendritic Cells Response to BacteriaFigure 5. Gram-negative bacteria do not break the tolerogenic properties of dexamethasone-DCs. Heat-killed bacteria were added at ratio 1:10 for 48 h to mo-DCs treated with dexamethasone or untreated 23727046 as a positive control. A. Phenotypic analysis revealed statistically significant reduction of CD83, CD86, and MHC I and class II expression. Maturation associated Rubusoside site molecules are depicted as mean fluorescent intensity of expression (MFI) of E. coli stimulated-DCs relative (fold-change expression) to control DCs without E. coli. (B) Cytokines produced by E. coli-stimulated DCs. Reduction of IL-12p70 (95.9 ; p,0.05), IL-23 (70.5 ; p,0.05) and TNF-a (40 ; p,0.05) and elevation of IL-10 (78 increase; p,0.05) in Gramnegative treated DCs. (C) Gram-negative stimulated DCs were cultured after being carefully washed with allogenic PBLs (ratio 1:20) for 7 days. The of proliferating cells was measured by CFSE dilution using flow cytometry. Significant allo-response inhibition of E. coli dex-DC (inhibition 28 ; p,0.05) compared to control DCs. IFN-c secretion was analyzed in the supernatant by standard ELISA. Results represent the mean and standard deviation of three independent donors. Student’s t-test: *p,0.05, **p,0.001. doi:10.1371/journal.pone.0052456.gintermediate CD80, CD83, CCR7, MHC class I and MHC class II expression. The high levels of CD86.Dition of immunosuppressive agents,pharmacological modulation, or inhibitory cytokines when DCs are being generated from monocytes influences the functional properties of the resulting DCs [9,10]. Several agents, including glucocorticoids [25] such as dexamethasone [26,27], mycophenolic acid [28], vitamin D3 (1a,25-dyhydroxyvitamin D3) [29], retinoic acid [30], the combination of dexamethasone and vitamin D3 [31], or IL-10 [32] have been used to render DCs resistant to maturation [33]. Tolerogenic DCs have been shown to induce T-cell anergy [34], suppress effector T cells, and promote 25033180 the generation of regulatory T cells (Tregs) [14,35]. Interestingly, some studies [14] have reported that the maturation of dex-conditioned DCs with LPS potentiates the tolerogenic phenotype of DCs. We performed a detailed phenotype analysis in order to compare iDCs and fully mature DCs with tol-DCs from healthy donors and patients with Crohn’s disease and address the stability of tol-DCs. DCs conditioned with dexamethasone displayed a semi-mature phenotype, which is consistent with the tolerogenic DC phenotypes described elsewhere [36]. We also observed an alteration in the DC maturation process; characterized by low-Tolerogenic Dendritic Cells Response to BacteriaFigure 4. Tol-DCs possess a stable phenotype. DCs were carefully washed to eliminate cytokines and dexamethasone, and viable DCs were further re-challenged with 100 ng/ml of LPS or 1 mg/ml of soluble CD40L as second stimuli. After 24 h, the phenotype (A) was analyzed by flow cytometry. Data represent relative MFI increase induced by LPS (n = 6) or CD40L (n = 4) compared to unstimulated iDCs, mDCs or tol-DCs as control. (B) IL-10 concentration is shown in pg/ml. IL-12p70 and IL-23 were not detected (detection limit = 7.8 pg/ml). Student’s t-test: *p,0.05, **p,0.001. (C) Tol-DCs do not recover the ability to stimulate T cells after re-challenge. T-cell proliferation was determined in triplicate by 3H-thymidine incorporation. IFN-c and IL-10 production in the supernatant was analyzed. doi:10.1371/journal.pone.0052456.gTolerogenic Dendritic Cells Response to BacteriaFigure 5. Gram-negative bacteria do not break the tolerogenic properties of dexamethasone-DCs. Heat-killed bacteria were added at ratio 1:10 for 48 h to mo-DCs treated with dexamethasone or untreated 23727046 as a positive control. A. Phenotypic analysis revealed statistically significant reduction of CD83, CD86, and MHC I and class II expression. Maturation associated molecules are depicted as mean fluorescent intensity of expression (MFI) of E. coli stimulated-DCs relative (fold-change expression) to control DCs without E. coli. (B) Cytokines produced by E. coli-stimulated DCs. Reduction of IL-12p70 (95.9 ; p,0.05), IL-23 (70.5 ; p,0.05) and TNF-a (40 ; p,0.05) and elevation of IL-10 (78 increase; p,0.05) in Gramnegative treated DCs. (C) Gram-negative stimulated DCs were cultured after being carefully washed with allogenic PBLs (ratio 1:20) for 7 days. The of proliferating cells was measured by CFSE dilution using flow cytometry. Significant allo-response inhibition of E. coli dex-DC (inhibition 28 ; p,0.05) compared to control DCs. IFN-c secretion was analyzed in the supernatant by standard ELISA. Results represent the mean and standard deviation of three independent donors. Student’s t-test: *p,0.05, **p,0.001. doi:10.1371/journal.pone.0052456.gintermediate CD80, CD83, CCR7, MHC class I and MHC class II expression. The high levels of CD86.