Can two human-derived Lactobacillus strains have opposite effects on TNF production?

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Researchers isolated human-derived lactobacilli from fecal samples of healthy volunteers. They selected 46 isolates from different volunteers to investigate their immunomodulatory properties. Conditioned medium from each isolate was assessed for its effect on tumor necrosis factor (TNF) production in lipopolysaccharide-activated THP-1 monocytes.

Of the 46 Lactobacillus isolates, 12 significantly inhibited TNF production to varying degrees. Strain TH58 had the strongest TNF-inhibitory activity, at 70% inhibition. In contrast, strain TH14 showed immunostimulatory activity by activating TNF production in THP-1 monocytes.

TH14 induced nuclear factor-kappaB (NF-kappaB) activation without lipopolysaccharide stimulation, whereas TH58 had no effect on NF-kappaB signaling whether or not lipopolysaccharide was present. Sequence analysis of their 16S rRNA genes identified TH58 as Lactobacillus saerimneri and TH14 as Lactobacillus ruminis.

The authors described this as the first report of a human isolate of L. saerimneri with TNF-inhibitory activity and of L. ruminis, a species indigenous to humans, with TNF-stimulatory activity. They suggested that the two strains could be candidates for use as immunoprobiotics.