The scientists, led by Professor Michiel Kleerebezem of NIZO Food Research, identified patterns of gene expressions in the cells of the intestinal wall that may trigger mechanism for immune tolerance.
The study is claimed to be the first scientific evidence of how probiotics influence the immune system in humans. The findings are published online in the Proceedings of the National Academy of Sciences (PNAS Online Early Edition).
A potential immune-enhancing effect from probiotic bacteria has been reported by many scientific groups, but the mechanism by how these effects may be occurring has not been elucidated, according to the Dutch researchers behind the new study.
Scientists from Top Institute Food and Nutrition, NIZO food research, Maastricht University, Wageningen UR, and Radboud University Nijmegen performed an in vivo human study in order to investigate the response of certain genes to Lactobacillus plantarum.
The randomised, double blind, placebo controlled, crossover study involved the ingestion of live L. plantarum, heat-killed L. plantarum, or placebo. Biopsies were taken from the duodenum of the subjects and their gene expression pattern analysed.
Using gene expression analysis, Prof Kleerebezem and his co-workers report differences between the expression profiles of people who consumed the live L. plantarum, compared to the heat-killed L. plantarum or placebo.
“Striking differences” in pathways dependent on a protein complex called nuclear factor kappa B (NF-kB) were observed. NF-kB plays an important role in the regulation of the immune system’s response to infection.
“Our in vivo study identified mucosal gene expression patterns and cellular pathways that correlated with the establishment of immune tolerance in healthy adults,” they concluded.
According the FAO/WHO, probiotics are defined as "live microorganisms which when administered in adequate amounts confer a health benefit on the host".
Immune-booster
In terms of boosting immune function, Lactobacillus fermentum was recently reported to boost the immune health of long distance runners, protecting them from respiratory illnesses. The Lactobacillus strain was associated with an enhancement in the activity of T cells, key players in the immune system (Br. J. Sports Med., doi 10.1136/bjsm.2007.044628)
Scientists at the Institute of Food Research (IFR) conducted a human study and reported that Lactobacillus casei Shirota may modulate the immune response to grass pollen, and help hay fever sufferers (Clin. Exp. Allergy, doi: 10.1111/j.1365-2222.2008.03025.x)
An improvement in the immune function of white blood cells in alcoholics has also been reported by a small study by researchers at University College London. This study also used Lactobacillus casei Shirota supplements (J. Hepatology, doi: 10.1016/j.jhep.2008.02.015)
Source: Proceedings of the National Academy of SciencesPublished online ahead of print 3 February 2009, doi:10.1073/pnas.0809919106"Differential NF-kappaB pathways induction by Lactobacillus plantarum in the duodenum of healthy humans correlating with immune tolerance"Authors: P. van Baarlen, F.J. Troost, S. van Hemert, C. van der Meer, W.M. de Vos, P.J. de Groot, G.J.E.J. Hooiveld, R.-J.M. Brummer, M. Kleerebezem