Induction of Regulatory T Cells by Human Dendritic Cells Treated with a Bacteria-Free Fermentation Product of Bifidobacterium Breve C50

RationaleSeveral studies have demonstrated that probiotic bacteria exert effects on the immune system. We have previously shown that a bacteria-free fermentation product of Bifidobacterium breve C50 (BbC50sn) induced an important IL-10 secretion by human dendritic cells (Hoarau et al., 2006). Our goal was to assess the ability of these dendritic cells to induce regulatory T cells.MethodsPurified CD4+CD25- human T cells were co-cultured with allogeneic BbC50sn-treated dendritic cells for 4 weeks. Then the T cell population (BbC50sn-T) was analysed: phenotypic characterization by flow cytometry, cytokine secretion in culture supernatant by ELISA and capacity to inhibit an allogeneic mixed leucocyte reaction (MLR) by 3H-Thymidine incorporation.ResultsAfter 4 weeks of co-culture with BbC50sn-DC, T lymphocytes were able to inhibit an allogeneic MLR (n = 12 experiments). Long-term cultured BbC50sn-T produced IL-10 and TGF-b in a significant rate. Moreover, BbC50sn-T expressed CD25 (about 50%±13%), GITR (about 20%±9%), and intracellular CTLA-4. About 5% of this population was positive for intracellular Foxp3 staining. In transwell assays, an immunosuppressive activity was observed only when BbC50sn-T were in contact with dendritic cells (n = 3). Thus, BbC50sn-T do not exert their suppressive activity through a T cell - T cell contact but seem to require the presence of dendritic cells to inhibit an allogeneic MLR.ConclusionsDendritic cells treated with a bacteria-free fermentation product of Bifidobacterium breve C50 can generate regulatory T cells. As far as we know, it is the first demonstration of regulatory T cell induction by a probiotic derivative product. RationaleSeveral studies have demonstrated that probiotic bacteria exert effects on the immune system. We have previously shown that a bacteria-free fermentation product of Bifidobacterium breve C50 (BbC50sn) induced an important IL-10 secretion by human dendritic cells (Hoarau et al., 2006). Our goal was to assess the ability of these dendritic cells to induce regulatory T cells. Several studies have demonstrated that probiotic bacteria exert effects on the immune system. We have previously shown that a bacteria-free fermentation product of Bifidobacterium breve C50 (BbC50sn) induced an important IL-10 secretion by human dendritic cells (Hoarau et al., 2006). Our goal was to assess the ability of these dendritic cells to induce regulatory T cells. MethodsPurified CD4+CD25- human T cells were co-cultured with allogeneic BbC50sn-treated dendritic cells for 4 weeks. Then the T cell population (BbC50sn-T) was analysed: phenotypic characterization by flow cytometry, cytokine secretion in culture supernatant by ELISA and capacity to inhibit an allogeneic mixed leucocyte reaction (MLR) by 3H-Thymidine incorporation. Purified CD4+CD25- human T cells were co-cultured with allogeneic BbC50sn-treated dendritic cells for 4 weeks. Then the T cell population (BbC50sn-T) was analysed: phenotypic characterization by flow cytometry, cytokine secretion in culture supernatant by ELISA and capacity to inhibit an allogeneic mixed leucocyte reaction (MLR) by 3H-Thymidine incorporation. ResultsAfter 4 weeks of co-culture with BbC50sn-DC, T lymphocytes were able to inhibit an allogeneic MLR (n = 12 experiments). Long-term cultured BbC50sn-T produced IL-10 and TGF-b in a significant rate. Moreover, BbC50sn-T expressed CD25 (about 50%±13%), GITR (about 20%±9%), and intracellular CTLA-4. About 5% of this population was positive for intracellular Foxp3 staining. In transwell assays, an immunosuppressive activity was observed only when BbC50sn-T were in contact with dendritic cells (n = 3). Thus, BbC50sn-T do not exert their suppressive activity through a T cell - T cell contact but seem to require the presence of dendritic cells to inhibit an allogeneic MLR. After 4 weeks of co-culture with BbC50sn-DC, T lymphocytes were able to inhibit an allogeneic MLR (n = 12 experiments). Long-term cultured BbC50sn-T produced IL-10 and TGF-b in a significant rate. Moreover, BbC50sn-T expressed CD25 (about 50%±13%), GITR (about 20%±9%), and intracellular CTLA-4. About 5% of this population was positive for intracellular Foxp3 staining. In transwell assays, an immunosuppressive activity was observed only when BbC50sn-T were in contact with dendritic cells (n = 3). Thus, BbC50sn-T do not exert their suppressive activity through a T cell - T cell contact but seem to require the presence of dendritic cells to inhibit an allogeneic MLR. ConclusionsDendritic cells treated with a bacteria-free fermentation product of Bifidobacterium breve C50 can generate regulatory T cells. As far as we know, it is the first demonstration of regulatory T cell induction by a probiotic derivative product. Dendritic cells treated with a bacteria-free fermentation product of Bifidobacterium breve C50 can generate regulatory T cells. As far as we know, it is the first demonstration of regulatory T cell induction by a probiotic derivative product.