Immune-stimulating effects of lactic acid bacteria in vivo and in vitro

Abstract

The health-promoting effects of lactic acid bacteria (LAB) are well recognised, making them a popular functional food ingredient. Commercially available probiotic products are often promoted as capable of improving immune defences also in healthy subjects. However, while strain-specific differences exist in the effects of LAB, conventional yoghurt bacteria have proved beneficial as well. For comparing the immunological effects of conventional and probiotic LAB, young healthy women received either a commercially available probiotic fermented milk product or a conventional yoghurt for four weeks. Both treatments showed comparable effects resulting in a stronger immunological reaction to stimuli (natural cytotoxicity against cancer cells, mitogen-induced T-lymphocyte activation and stimulated cytokine production). To study the mechanisms behind these effects, conventional (Lactobacillus delbrueckii) and probiotic (Lactobacillus rhamnosus GG), LAB were compared in vitro at the cellular level. Interestingly, L. rhamnosus GG was more potent in inducing maturation of dendritic cells (DC) that play a substantial role in directing the immune response to stimuli. In turn, L. delbrueckii provoked a higher secretion of proinflammatory cytokines as well as IL-10. These effects were, however, observed only after direct incubation of DC and LAB, not when both were separated by a layer of enterocyte-like Caco-2 cells. LAB also induced cytokine secretion in peripheral blood mononuclear cells in a similar manner and this effect was reduced in a Caco-2 cell model, suggesting a modulating influence of gut epithelial cells. While both conventional and probiotic strains modulate the immune response, specific properties may offer therapeutic options in the treatment of certain diseases.

The Gut Microbiome and the Brain

“…121 A study of college students undergoing the stress of final examinations found a decrease in the relative concentration of lactic acid bacteria in feces after the examination 122 (speciation was not performed). Since lactic acid bacteria have immunomodulating effects 123,124 and may influence the broader composition of the gut microbiome, 125 it seems likely that humans respond to psychosocial stress with responses that are comparable to, if distinct from, the reactions of laboratory animals.…”

Promising Immunomodulatory Effects of Selected Strains of Dairy Propionibacteria as Evidenced In Vitro and In Vivo

“…However, little is known about the immunomodulatory potential of highly consumed starter bacteria such as dairy propionibacteria. Consumption of fermented products has an impact on immune system function (25), and the bacterial content of these products is responsible for immunomodulation (6,10). Dairy propionibacteria display various probiotic properties either similar to or distinct from those reported for probiotic bifidobacteria and lactic acid bacteria (3).…”

Probiotic: effectiveness nutrition in cancer treatment and prevention

“…There is evidence suggesting that some probiotics strains can affect the host's immunologic response, stimulating anti-inflammatory cytokines, antioxidants compounds, and generating anti-carcinogenic compounds (25). Thus, probiotics emerge as great alternatives for prevention, and treatment of a variety of gastroenterological conditions, for instance, inflammatory bowel disease, and colorectal cancer (26,27).…”