There is considerable interest in the strain specificity of immune modulation by probiotics. The present study compared the immunomodulatory properties of six probiotic strains of different species and two genera in a human peripheral blood mononuclear cell (PBMC) model in vitro. Live cells of lactobacilli (Lactobacillus casei Shirota, L. rhamnosus GG, L. plantarum NCIMB 8826 and L. reuteri NCIMB 11951) and bifidobacteria (Bifidobacterium longum SP 07/3 and B. bifidum MF 20/5) were individually incubated with PBMC from seven healthy subjects for 24 h. Probiotic strains increased the proportion of CD69 þ on lymphocytes, T cells, T cell subsets and natural killer (NK) cells, and increased the proportion of CD25 þ , mainly on lymphocytes and NK cells. The effects on activation marker expression did not appear to be strain specific. NK cell activity was significantly increased by all six strains, without any significant difference between strains. Probiotic strains increased production of IL-1b, IL-6, IL-10, TNF-a, granulocyte-macrophage colony-stimulating factor and macrophage inflammatory protein 1a to different extents, but had no effect on the production of IL-2, IL-4, IL-5 or TNF-b. The cytokines that showed strain-specific modulation included IL-10, interferon-g, TNF-a, IL-12p70, IL-6 and monocyte chemotactic protein-1. The Lactobacillus strains tended to promote T helper 1 cytokines, whereas bifidobacterial strains tended to produce a more anti-inflammatory profile. The results suggest that there was limited evidence of strain-specific effects of probiotics with respect to T cell and NK cell activation or NK cell activity, whereas production of some cytokines was differentially influenced by probiotic strains.

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Consumption of a probiotic drink containing LcS improved NK cell activity and tended to produce a more anti-inflammatory cytokine profile in an older population.

SummaryModulation of host immunity is an important potential mechanism by which probiotics confer health benefits. This study was designed to investigate the effects of a probiotic strain, Lactobacillus casei Shirota (LcS), on immune function using human peripheral blood mononuclear cells (PBMC) in vitro. In addition, the role of monocytes in LcS-induced immunity was also explored. LcS promoted natural killer (NK) cell activity and preferentially induced expression of CD69 and CD25 on CD8+ and CD56 + subsets in the absence of any other stimulus. LcS also induced production of interleukin (IL)-1b, IL-6, tumour necrosis factor (TNF)-a, IL-12 and IL-10 in the absence of lipopolysaccharide (LPS). In the presence of LPS, LcS enhanced IL-1b production but inhibited LPS-induced IL-10 and IL-6 production, and had no further effect on TNF-a and IL-12 production. Monocyte depletion reduced significantly the impact of LcS on lymphocyte activation, cytokine production and natural killer (NK) cell activity. In conclusion, LcS activated cytotoxic lymphocytes preferentially in both the innate and specific immune systems, which suggests that LcS could potentiate the destruction of infected cells in the body. LcS also induced both proinflammatory and anti-inflammatory cytokine production in the absence of LPS, but in some cases inhibited LPSinduced cytokine production. Monocytes play an important role in LcSinduced immunological responses.

OPF consumed with breakfast may lower postprandial glycemic and insulinemic responses to typical meal ingestion in men with increased cardiometabolic risk. This trial is registered at clinicaltrials.gov as NCT01963416.