Immunostimulatory effect of faecal Bifidobacterium species of breast-fed and formula-fed infants in a PBMC/CaCO-2 coculture system

Bifidobacterium spp. typical of the human intestinal microbiota are believed to influence the balance of immune responses in the intestinal mucosa. Aim: To investigate the effect of different bifidobacterial species and mixtures of them in in vitro experiments with PBMCs and CaCo-2 cells. Methods: Bifidobacterium adolescentis; Bifidobacterium angulatum; Bifidobacterium breve; Bifidobacterium catenulatum; Bifidobacterium infantis; Bifidobacterium longum; and two combinations of these bifidobacteria simulating the species composition found in fecal samples from breast fed (BF) and formula fed (FF) infants were used. The levels of several cytokines were measured by direct stimulation of PBMCs and by stimulation of a Caco-2/PBMCs co-culture with bifidobacteria. Results: B. catenulatum and B. breve were the strongest enhancers of IFN-γ, production by direct stimulation of PBMCs. B. longum was the highest inducer of IL-10 and the lowest TNF-α stimulus. In the Caco-2/PBMC system, B. breve was the highest inducer of IL-8 production by Caco-2 cells; significantly different from B. infantis, B. adolescentis and the FF mixture (p<0·05). IFN-γ produced by PBMCs stimulated with the BF mixture (containing 22% B. breve, compared to 7% in FF mixture) was significantly higher compared to B. adolescentis, B. infantis, and B. longum. B. adolescentis also inhibited IFN-γ production compared to FF mixture and B. longum. Conclusions: The proportion of different Bifidobacterium strains seems to be an important determinant of the cytokine balance in the simulated intestinal environment studied. B. breve and the combination of the Bifidobacterium species typically found in the microbiota of breast-fed infants have shown the most significant effects.

Peer reviewed