Abstract
BACKGROUND Several clinical trials suggest that probiotics may have a role in the prevention of eczema. The optimal timing and mechanisms underlying this intervention are not clear. In particular it is not known whether such treatment works during pregnancy or whether postnatal exposure is important. OBJECTIVE We investigated whether the probiotic Lactobacillus rhamnosus strain GG (LGG) influences fetal immune responses when administered to pregnant women, as a possible mechanism for its protective effects against the development of eczema. METHODS Peripheral blood mononuclear cell from 11 adults treated with LGG, and cord blood mononuclear cells (CBMCs) from 73 women participating in a randomized controlled trial of LGG treatment were cultured with heat-killed LGG, ovalbumin (OVA) or without stimulus. Cells were analysed by flow cytometry and real-time PCR for markers of dendritic cell (DC) phenotype, T cell proliferation and regulation. Cytokine secretion was analysed in culture supernatants by multiplex cytokine assay. RESULTS LGG treatment of adults led to systemic immune responses suggestive of antigen-specific tolerance including reduced CD4(+) T cell proliferation to heat-killed LGG (30% reduction; P=0.03). LGG treatment of pregnant women did not influence CD4(+) T cell proliferation, forkhead box P3 expression, DC phenotype or cytokine secretion in CBMCs cultured with heat-killed LGG or OVA. CONCLUSION LGG treatment of pregnant women fails to influence fetal antigen-specific immune responses. This suggests that modulation of fetal immune responses may not be a major mechanism by which probiotics such as LGG prevent eczema.
