Two strains of probiotic Lactobacillus enhance immune response and promote naive T cell polarization to Th1

We co-cultured Caco-2 cells with Lactobacillus salivarius and L. plantarum in vitro to investigate their immunoregulatory mechanisms and detected Lactobacillus strains adhering to Caco-2 cells expressing mRNAs of cytokines and Toll-like receptors (TLRs) by fluorescent quantitative reverse transcription-polymerase chain reaction. The strains were intragastrically administered to mice. Thymus/spleen indexes were measured on different days. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, flow cytometry, and enzyme-linked immunosorbent assay were performed to assess different variables. Results showed increased mRNA expressions of T helper 1 (Th1), various cytokines, surface receptors, TLRs (2, 4, and 9), thymus/spleen indexes, spleen lymphocyte transformation rate, macrophage energy metabolism and phagocytosis, CD11c(+)CD80(+) cell number, interferon-gamma secretion, and sIgA secretion levels; inhibition of nuclear factor-kappa B inflammation signal pathway; and downregulated mRNA expression of specific interleukins. Both Lactobacillus strains can promote naive T cell differentiation (Th1) and participate in immunomodulatory responses, featuring a potential in prevention and management approaches for foodborne diseases.