Effects of bifidobacterial cytoplasm, cell wall and exopolysaccharide on mouse lymphocyte proliferation and cytokine production

Probiotic bifidobacteria have been reported to stimulate the immune system and thus offer the possibility of improving host immune defense against pathogens. The aim of this work was to study the effects of bifidobacterial cytoplasm, cell wall, and exopolysaccharide (EPS) on splenocyte proliferation and production of -IFN-γγ and IL-10. Three bifidobacteria, RBL64, RBL81, and RBL82 isolated from newborn infant faeces were used in our study. Commercial strain Bifidobacterium lactis Bb12 was used as a positive control. Among different cell extracts, the cell wall components showed the most profound effects on cell proliferation and cytokine production. EPS neither stimulated lymphocyte proliferation nor induced cytokine secretion. B. lactis   Bb12 exhibited a significant immunostimulating effect (stimulation index=16) compared with other bifidobacteria studied. More -IFN-γγ (>4 ng mL−1) was produced in response to cell wall and about 0.8 ng mL−1 of IL-10 was detected in the cell culture supernatant. The results demonstrate that bifidobacterial extracts, mainly the cell walls, stimulate the proliferation of lymphocytes and suggest that such extracts could be used in controlling certain immune pathologies.