Consumption of probiotics increases the effect of regulatory T cells in transfer colitis.

BACKGROUND: Probiotics may alter immune regulation. Recently, we showed that the probiotic bacteria Lactobacillus acidophilus NCFM™ influenced the activity of regulatory T cells (Tregs) in vitro. The aim of the present work was to demonstrate if L. acidophilus NCFM™ also affects the function of Tregs in vivo. METHODS: Development of colitis after transfer of CD4+CD25- T cells and protection from colitis by Tregs was studied in immunodeficient SCID mice which were simultaneously tube-fed with L. acidophilus NCFM™ or L. salivarius Ls-33 for 5 weeks. RESULTS: Probiotic-fed SCID mice transplanted with low numbers of Tregs in addition to the disease-inducing T cells were completely protected from colitis. This was in contrast to the control group, which showed intermediate levels of inflammation. In addition, feeding with probiotics lowered serum levels of inflammatory cytokines in both colitic mice and in mice protected from colitis by Tregs. Gene expression patterns of rectum samples of protected mice that receive either one of the probiotics showed a closer resemblance to naïve SCID mice than did patterns of the control group. The mechanism of action of the probiotics appears to be an indirect effect by inducing a Treg-favorable environment rather than a direct effect on the Tregs. CONCLUSIONS: L. acidophilus NCFM™ and L. salivarius Ls-33 feeding of SCID mice increases the in vivo effect of Tregs, resulting in a gene expression pattern in the rectum resembling that of the naïve SCID mouse.

Antigen-presenting cells exposed to Lactobacillus acidophilus NCFM, Bifidobacterium bifidum BI-98, and BI-504 reduce regulatory T cell activity.

BACKGROUND: The effect in vitro of six different probiotic strains including Lactobacillus acidophilus NCFM, Lactobacillus salivarius Ls-33, Lactobacillus paracasei subsp. paracasei YS8866441, Lactobacillus plantarum Lp-115, Bifidobacterium bifidum BI-504 and BI-98 was studied on splenic enteroantigen-presenting cells (APC) and CD4(+)CD25(+) T-regulatory cells (Tregs) in splenocyte-T cell proliferation assays. METHODS: Splenocytes exposed to enteroantigen +/- probiotics were used to stimulate cultured CD4(+)CD25(-) T cells to which titrated numbers of Tregs were added. Cytokine assays were performed by use of neutralizing antibodies and ELISA. RESULTS: Exposure of APCs to enteroantigens and the series of probiotic strains mentioned above did not influence the stimulatory capacity of APCs on proliferative enteroantigen-specific T cells. However, exposure to B. bifidum BI-98, BI-504 and L. acidophilus NCFM consistently reduced the suppressive activity of Tregs. The suppressive activity was analyzed using fractionated components of the probiotics, and showed that a component of the cell wall is responsible for the decreased Treg activity in the system. The probiotic-induced suppression of Treg function is not mediated by changes in APC-secretion of the inflammatory cytokines IL-6 or IL-1b. CONCLUSION: We conclude that certain probiotic strains can modify APCs to cause reduced Treg activity. This effect apparently depends on a direct APC-to-Treg cell contact. The APC-mediated suppressive effect on Treg function of certain probiotic strains may constrain the anti-inflammatory activity, which is often desired from probiotic therapy. This unexpected function of certain probiotic strains should be taken into consideration when designing adjuvant therapies with these bacteria, or when probiotic strains are selected for improvement of gut-associated inflammation like IBD.

Identification of a microRNA signature in dendritic cell vaccines for cancer immunotherapy.

Dendritic cells (DCs) exposed to tumor antigens followed by treatment with T(h)1-polarizing differentiation signals have paved the way for the development of DC-based cancer vaccines. Critical parameters for assessment of the optimal functional state of DCs and prediction of the vaccine potency of activated DCs have in the past been based on measurements of differentiation surface markers like HLA-DR, CD80, CD83, CD86, and CCR7 and the level of secreted cytokines like interleukin-12p70. However, the level of these markers does not provide a complete picture of the DC phenotype and may be insufficient for prediction of clinical outcome for DC-based therapy. We therefore looked for additional biomarkers by investigating the differential expression of microRNAs (miRNAs) in mature DCs relative to immature DCs. A microarray-based screening revealed that 12 miRNAs were differentially expressed in the two DC phenotypes. Of these, four miRNAs, hsa-miR-155, hsa-miR-146a, hsa-miR-125a-5p, and hsa-miR-29a, were validated by real-time polymerase chain reaction and northern blotting. The matured DCs from 12 individual donors were divided into two groups of highly and less differentiated DCs, respectively. A pronounced difference at the level of miRNA induction between these two groups was observed, suggesting that quantitative evaluation of selected miRNAs potentially can predict the immunogenicity of DC vaccines.

Sensitivity to growth suppression by 1alpha,25-dihydroxyvitamin D(3) among MCF-7 clones correlates with Vitamin D receptor protein induction.

The antiproliferative effect of 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) has been studied for a decade in diverse model systems, but the signalling pathways linking 1alpha,25(OH)(2)D(3) to cell cycle arrest remains unclear. In our attempt to establish a model system which would allow further identification of important players in the process of the 1alpha,25(OH)(2)D(3) imposed cell cycle arrest, we have isolated derivatives of the human breast cancer cell line MCF-7 and chosen two nearly 1alpha,25(OH)(2)D(3) resistant and two hypersensitive sub-clones. Investigation of cell cycle proteins regulated by 1alpha,25(OH)(2)D(3) in these clones indicates that activation of one component/pathway is responsible for the linkage between 1alpha,25(OH)(2)D(3) and growth arrest. Protein levels of the Vitamin D receptor (VDR) were elevated in sensitive cells upon 1alpha,25(OH)(2)D(3) treatment, whereas resistant clones were unable to induce VDR upon 1alpha,25(OH)(2)D(3) treatment. Our data show that VDR protein levels and the ability of a cell to induce VDR upon 1alpha,25(OH)(2)D(3) treatment correlate with the antiproliferative effects of 1alpha,25(OH)(2)D(3), and suggest that the level of VDR in cancer cells might serve as a prognostic marker for treatment of cancer with 1alpha,25(OH)(2)D(3) analogues.