Dirt may be the best thing for you
Via Science Daily, another report on the importance of dirt in our lives, and published in the Journal of Allergy and Clinical Immunology. This is of course hot on the heels of our last dirt-related update, suggesting that we shouldn’t overlook what can be found all around us. The current report, from the University of Copenhagen, describes the importance of immune system challenges early in life, and how these formative challenges can aid in the resistance to allergies later in life.
The Danish study followed a cohort of 411 children over 6 years, for 6 month health assessments and analysis of their normal microbial flora. Bacteria were analyzed by sequencing ribosomal RNA, and used to assess the complexity of the flora. The authors found that the diversity of microbial flora was inversely related to the risk of allergic sensitization as determined by serum IgE levels, skin prick test, blood eosinophil levels, and allergic rhinitis. There was no association with the development of asthma however. The authors conclude from this extensive study that lack of diversity in the early intestinal microbiome can significantly the development of a number of “lifestyle-related disorders.”
Commentary and an interview with the authors in Science Daily also expanded on the study. We have discussed in class that the intestinal microbiome is acquired during the birth process, and that the manner of birth (vaginal vs. cesarean) can influence this initial acquisition. Babies born by cesarean delivery obtain their normal intestinal flora slightly later than vaginally-delivered babies (weeks to months later), and do so from exclusively from their initial meals. Epidemiological studies have shown that these babies develop allergies far more commonly. Although the species of bacteria found in both groups is not significantly different, the timing appears to be important.
The basis of this phenomenon is something that I’ve periodically presented in Micro before, using the analogy of my dog who needs to have something to do at all times. As with most dogs, if you don’t give them a task, they will find a task on their own. Aspects of our immune system are to some extent underutilized, due to our more fastidious lifestyle in comparison to earlier generations. Consequently, like the dog, if they do not have a given task to do they find something else to do, which may in fact be undesired.
This principle is known as “helminthic therapy“, and there is a fair amount of experimental evidence supporting it, and there has been a previous BIO230 posting presenting a related approach with worms to block infection. With this, disease symptoms for a variety of maladies can be diminished or eliminated by co-infection with helminths, or worms. These parasites are not typically encountered by us anymore, however they were very prevalent previously. Our major innate and adaptive immune response to these parasites is via inflammatory mediators and IgE; if those parasites are not encountered, those mediators remain unchallenged, and it is thought that inappropriate and coincidental triggers cause them to become active in the absence of their “normal” stimulus. Helminthic therapy involves re-introducing those normal stimuli into a patient with the inappropriate (allergic) response, and this therapy has been found to be effective at greatly diminishing the allergic response.