Role of interleukin (IL‐10) in probiotic‐mediated immune modulation: an assessment in wild‐type and IL‐10 knock‐out mice

Summary While the impact of Bifidobacterium infantis 35624 and other probiotics on cytokines has been shown in established colitis, the effects of B. infantis consumption in pre‐inflammation of interleukin (IL)‐10 knock‐out (KO) mice and on the wild‐type (WT) C57Bl/6 mice have not been well demonstrated. The objective of this study was to examine cytokine responses in mucosal and systemic lymphoid compartments of IL‐10 KO mice early in disease and to compare with control WT mice. Mice were fed B. infantis or placebo for 5 weeks and culled prior to the onset of chronic intestinal inflammation (12–14 weeks). The spleen, Peyer's patches and intestinal mucosa were removed and stimulated with various bacterial stimuli. Cytokine levels were measured by enzyme‐linked immunosorbent assay. While basal intestinal and systemic cytokine profiles of WT and IL‐10 KO mice were similar, transforming growth factor (TGF)‐β was reduced in the spleen of IL‐10 KO mice. Following probiotic consumption, interferon (IFN)‐γ was reduced in the Peyer's patch of both WT and IL‐10 KO mice. Alterations in IFN‐γ in the Peyer's patches of WT mice (enhancement) versus IL‐10 KO (reduction) were observed following in vitro stimulation with salmonella. Differential IL‐12p40, CCL2 and CCL5 responses were also observed in IL‐10 KO mice and WT mice. The cytokine profile of IL‐10 KO mice in early disease was similar to that of WT mice. The most pronounced changes occurred in the Peyer's patch of IL‐10 KO mice, suggesting a probiotic mechanism of action independent of IL‐10. This study provides a rationale for the use of B. infantis 35624 for the treatment of gastrointestinal inflammation.