The Effects of Single Strains and Mixtures of Probiotic Bacteria on Immune Profile in Liver, Spleen, and Peripheral Blood

Probiotic bacteria have potential use as immunomodulators but comparative data on their immunological effects are very limited. The aim of this study was to characterize the effect of oral administration of probiotic strains, alone or as mixtures, on systemic and organ-specific immune responses. For this purpose, healthy C57BL/6 mice were perorally administered probiotics for 3 weeks. A total of five common probiotic strains, Lactobacillus rhamnosus species GG (LGG) and LC705, Bifidobacterium breve 99 (Bb99), Propionibacterium freudenreichii Shermanii JS (PJS), and Escherichia coli Nissle 1917 (EcN), and two of their mixtures, were tested. Livers, spleens, and blood were collected for investigation. A number of five treatments increased the abundance of the natural killer (NK) cells. Bb99 had the most prominent effect on hepatic NK cells (20.0 ± 1.8%). LGG (liver: 5.8 ± 1.0%; spleen: 1.6 ± 0.4%), Bb99 (liver: 13.9 ± 4.3%; spleen: 10.3 ± 3.7%), and EcN (liver: 8.5 ± 3.2%; spleen: 1.0 ± 0.2%) increased the percentage of both the hepatic and splenic T-helper 17 cells. Moreover, LGG (85.5 ± 3.0%) and EcN (89.6 ± 1.2%) increased the percentage of splenic regulatory T-cells. The tested mixtures of the probiotics had different immunological effects from their individual components on cell-mediated responses and cytokine production. In conclusion, our results confirm that the immunomodulatory potential of the probiotics is strain- and organ/tissue-specific, and the effects of probiotic mixtures cannot be predicted based on their single constituents.