Download Biodiversity hypothesis and immune dysfunction –impications for the

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WAO Hyderabad 7. December 2012
Symposium 6. The environment and occupational allergies
Biodiversity and allergy
Nature gets poor, we get sick
Tari Haahtela, Professor, Helsinki University, Finland, email: [email protected]
Although the Convention of Biological Diversity (1) is primarily concerned with plants and
animals, biodiversity also includes micro-organisms, which are less visible but comprise the
bulk of living matter on our Earth (2). We have proposed that biodiversity at the level of
macrobiota and microbiota are interrelated in that biodiversity loss of the former is likely to
be associated with loss of diversity of the latter (3).
Environmental biodiversity, human microbiota and allergy are interrelated (4).We studied
118 randomly selected teenagers from northeastern Finland. The participants were screened
for allergy, and skin swabs were taken from the forearm to identify the composition of the
skin microbiota. The environment surrounding the homes was recorded, and plant species in
the yard identified.
Participants who lived on farms or near forests had a different composition of bacteria on their
skin and were less sensitive to allergens than those who had less contact with the natural
environment. In healthy teenagers certain gammaproteobacteria on the skin were positively
associated with the level of an important anti-inflammatory signaling molecule, interleukin-10
in the blood.
These results imply that a high genetic diversity of gammaproteobacteria on the skin is linked
to increased tolerance against allergens. Gammaproteobacteria are found in the soil, on plant
surfaces, on grass pollen, and on dust. The surroundings of healthy teenagers contained 25 %
more uncommon native flowering plant species than the surroundings of allergic teenagers.
The Finnish and German observations uniformly indicate, that high environmental bacterial
diversity is allergy protective (4,5). Gammaproteobacteria are probably just one example of
active commensals having an effect on immunoregulatory circuits and promoting healthy
immune balance.
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The two global megatrends, biodiversity loss (altered biosphere), and the increased prevalence
of inflammatory diseases, may be closely linked. Inflammation is a cardinal feature not only
of asthma and allergy, but also of autoimmune diseases, many forms of cancer, and has also
been linked with depression and obesity.
The concept of inducing tolerance and homeostasis may become a prime target for prevention
and treatment strategies for many diseases of the modern time in which dysregulation of the
immune system plays an essential role. For example, in allergy treatment, inducing immune
tolerance to allergens is characterized by establishment of a long-term clinical recovery.
United Nations estimated recently, that in 30 years time 80 % of human populations live in
cities implying less contact with nature. This is significant for public health, as our study
implies that contact with natural environments rich in species is a prerequisite to balanced
immune function. Environmental micro-organisms, previously ubiquitous and abundantly
present e.g. in drinking water and milk, are key players for the induction and maintenance of
immunoregulatory circuits and tolerance.
References
1. Convention on Biological Diversity 1992. www.biodiv.org/convention/
2. Whitman WB, Coleman DC, Wiebe WJ. Prokaryotes: the unseen majority. Proc Natl Acad Sci
USA 1998;95:6578-83.
3. von Hertzen L, Hanski I, Haahtela T. Biodiversity loss and rising trends of inflammatory
diseases: two global megatrends that may be related. EMBO Reports 2011;12:1089-93.
4. Hanski I, von Hertzen L, Fyhrquist N, Koskinen K,Torppa K, Laatikainen T, Karisola,P,
Auvinen P, Paulin L, Mäkelä, MJ, Vartiainen E, Kosunen TU, Alenius H, Haahtela, T.
Environmental biodiversity, human microbiota, and allergy are interrelated. Proc Natl Acad
Sci USA 2012;109:8334-9.
5. Alenius H, Pakarinen J, Saris O, Andersson MA, Leino M, Sirola K, Majuri ML, Niemela J,
Matikainen S, Wolff H, von Hertzen L, Makela M, Haahtela T, Salkinoja-Salonen M.
Contrasting immunological effects of two disparate dusts - preliminary observations. Int
Arch Allergy Immunol 2009;149:81-90.
6. Ege MJ, Mayer M, Normand AC, Genuneit J, Cookson WO, Braun-Fahrländer C, Heederik
D, Piarroux R, von Mutius E; GABRIELA Transregio 22 Study Group. Exposure to
environmental microorganisms and childhood asthma. N Engl J Med 2011;364:701-9.
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