Despite the fact that the value of probiotics is very controversial in scientific community, it exists some scientific arguments and results in mouse and human models that are exiting our knowledge and our thought. In this work, we examined the effects of probiotic supernatant on the dendritic cell (DC) maturation. The DC are the only one cell able to activate naïve T lymphocytes and to drive the Th1/Th2 orientation through a specific cytokine profile secretion. We hypothesized that supernatant of Bifidobacteria breve C50 (BbC50), that have exhibited probiotic activity in mice, could interact directly with DC to explain probiotic activity.

In a model of human monocyte derived DC, we tested several BbC50 supernatants at increased doses on DC, followed by cytometry and proliferative assays.

Addition of probiotic supernatants (100μg/ml) induced maturation of DC, evidenced by the increase of maturated markers surface expression (CD83, CD86 and HLA-DR) and IL12 synthesis. Moreover, the DC allostimulatory capacity on CD4+ human T cells was enhanced in the presence of BbC50 supernatant. Both maturation markers and allo-stimulation capacity were independent of LPS contamination, demonstrated by the addition of polymixin B. We further examined the cytokine orientation of human CD4+ cells in a DC coculture with probiotic.

BbC50 supernatant demonstrated immunomodulatory capacities on human DC, opening prospects in the prevention of allergic diseases.