Certain therapeutic microbes, including Bifidobacteria infantis (B. infantis) 35624 exert beneficial immunoregulatory effects by mimicking commensal-immune interactions; however, the value of these effects in patients with non-gastrointestinal inflammatory conditions remains unclear. In this study, we assessed the impact of
oral administration of B. infantis 35624, for 6‒8 weeks on inflammatory
biomarker and plasma
cytokine levels in patients with
ulcerative colitis (UC) (n = 22),
chronic fatigue syndrome (CFS) (n = 48) and
psoriasis (n = 26) in three separate randomized, double-blind, placebo-controlled interventions. Additionally, the effect of B. infantis 35624 on immunological
biomarkers in healthy subjects (n = 22) was assessed. At baseline, both gastrointestinal (UC) and non-gastrointestinal (CFS and
psoriasis) patients had significantly increased plasma levels of
C-reactive protein (CRP) and the pro-inflammatory
cytokines tumor necrosis factor α (TNF-α) and
interleukin-6 (IL-6) compared with healthy volunteers. B. infantis 35624 feeding resulted in reduced plasma CRP levels in all three inflammatory disorders compared with placebo. Interestingly, plasma TNF-α was reduced in CFS and
psoriasis while
IL-6 was reduced in UC and CFS. Furthermore, in healthy subjects, LPS-stimulated TNF-α and
IL-6 secretion by peripheral blood mononuclear cells (PBMCs) was significantly reduced in the B. infantis 35624-treated groups compared with placebo following eight weeks of feeding. These results demonstrate the ability of this microbe to reduce systemic pro-inflammatory
biomarkers in both gastrointestinal and non-gastrointestinal conditions. In conclusion, these data show that the immunomodulatory effects of the microbiota in humans are not limited to the mucosal immune system but extend to the systemic immune system.