Immunomodulatory effects of Lactobacillus rhamnosus GG on dendritic cells, macrophages and monocytes from healthy donors

• We study immunomodulation of L. rhamnosus GG on antigen-presenting cells.
• L. rhamnosus GG increased Th1-associated but decreased Th2-associated cytokines.
• Anti-inflammatory effects of L. rhamnosus GG was seen on monocytes.
• L. rhamnosus GG reduced TLR2 and TLR8 mRNA levels of antigen-presenting cells.

Lactobacillus rhamnosus GG (LGG) is clinically documented in relieving and preventing diarrhea, childhood infections, allergies and atopic eczema but knowledge of its immunomodulatory properties on antigen-presenting cells (APCs) is lacking. Here, immunomodulation of LGG on dendritic cells (DCs), macrophages and monocytes was investigated. Toll-like receptor (TLR) mRNA levels and immunophenotype of LGG-treated APCs, and cytokine secretion levels of culture of LGG-treated DCs and peripheral blood mononuclear cells were examined. LGG reduced TLR 8 mRNA level of APCs, implying that the immunomodulation of LGG may be partly due to the reaction of RNA with APCs. LGG reduced CD16 expression on macrophages and CD11b expression on monocytes. The results obtained demonstrated the effect of LGG on type-1 immune response polarization as observed from elevated production of IL-12 and TNFα across different APC stimulation models, suggesting that LGG may have immunotherapeutic potential in ameliorating and preventing the development of Th2-mediated inflammatory diseases and against infections.