The Evolution & Medicine Review

Sanitizing the hygiene hypothesis (Workshop Report)

Sanitizing the hygiene hypothesis:
Health lessons from human co-evolution with microorganisms

Report from a Workshop led by
Kathleen Barnes, Department of Medicine,
Johns Hopkins University and
Erika von
Mutius, Professor of Pediatrics, University Children’s Hospital, Munich

One of five workshops in a conference on
Evolution and Diseases of Modern Environments
Organized by Randolph Nesse, at the Berlin Charité,  October 13-14, 2009
In conjunction with The World Health Summit
Sponsored by the Volkswagen Foundation

Introduction: There is a large body of research work addressing the potential beneficial role of microbial exposures for the development of asthma, allergies and autoimmune disorders. A seminal publication by David Strachan in 1989 coined the ‘hygiene hypothesis’ in an attempt to explain his observation of protection from hay fever when having many older siblings. The ‘hygiene hypothesis’ has since undergone numerous revisions and alterations with respect to potential underlying immunological mechanisms, the type of infectious / microbial stimuli and the potential link to autoimmune diseases. It has become apparent over the years that many open research questions have not been answered; therefore, we have drafted a qualitative overview on the existing evidence of a protective effect of microbial exposures for the onset of asthma, allergies and autoimmune diseases.

Evidence: The Working Group agreed there is compelling evidence from population-based studies in humans to suggest that the ‘hygiene hypothesis’ may be operative in asthma, allergies, SLE, sarcoidosis, and ankylosing spondylitis, and suggestive evidence exists for type I diabetes, inflammatory bowel disease (IBD) and multiple sclerosis. (more…)

Genes essential to the immune system that are “entrusted” to microbial “Old Friends”

In 2005 Sarkis Mazmanian and colleagues showed that a single polysaccharide from an intestinal commensal, Bacteroides fragilis, could largely correct the subnormal and functionally distorted development of the immune system that occurs in germ-free mice (Mazmanian et al. 2005). More recently they have shown, using three different models of intestinal inflammation, that the same polysaccharide, given by mouth, can turn on crucial immunoregulatory pathways (Mazmanian et al. 2008). In the discussion of the latter paper they state:- (more…)