Generation of tolerogenic dendritic cells using Lactobacillus rhamnosus and Lactobacillus delbrueckii as tolerogenic probiotics

Systemic lupus erythematosus (SLE) concurs with excessive uncontrolled inflammatory immune responses that lead to the loss of immune tolerance. Dendritic cells (DCs) are important and determinant immune cells that regulate immune responses. Tolerogenic DCs with regulatory markers and cytokines could induce regulatory immune cells and responses. Tolerogenic probiotics are capable of producing regulatory DCs from monocytes in in vitro conditions. The purpose of this study was to evaluate the effect of Lactobacillus delbrueckii and Lactobacillus rhamnosus on the production of DCs in an in vitro condition. Peripheral blood mononuclear cellswere isolated from the healthy and SLE donors. Monocytes were cultured with optimized concentrations of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 4 (IL-4) to produce immature DCs (IDCs). An IDC uptake assay was performed, and IDCs of healthy and SLE donors were divided into three subgroups following 48 hours of treatment with GM-CSF and IL-4, along with L. delbrueckii, L. rhamnosus, and mixed probiotics for the production of tolerogenic DCs. The surface expression of Human Leukocyte Antigen-antigen D Related (HLA-DR), CD86, CD80, CD83, CD1a, and CD14 was analyzed using flow cytometry, and the gene expression levels of indoleamine 2,3-dioxygenase (IDO), IL-10, and IL-12 were measured using real-timepolymerase chain reaction. We observed significantly reduced expression of costimulatory molecules and other surface markers in the probiotic-induced mature DCs (MDCs) in both healthy and SLE donor groups in comparison with lipopolysaccharide (LPS)-induced MDCs. In addition, the expression of IDO and IL-10 increased, whereas IL-12 decreased significantly in probiotic-induced MDCs compared with LPS-induced MDCs. IDCs and especially mature tolerogenic DC of SLE patients highly expressed IDO. The results of the current study suggested that live probiotics could modify properties of DCs to modulatory cells, which might contribute to the induction of tolerance and renovation of immune hemostasis.