title: Environmental biodiversity, human microbiota, and allergy are interrelated.
abstract: Rapidly declining biodiversity may be a contributing factor to another global megatrend--the rapidly increasing prevalence of allergies and other chronic inflammatory diseases among urban populations worldwide. According to the "biodiversity hypothesis," reduced contact of people with natural environmental features and biodiversity may adversely affect the human commensal microbiota and its immunomodulatory capacity. Analyzing atopic sensitization (i.e., allergic disposition) in a random sample of adolescents living in a heterogeneous region of 100 × 150 km, we show that environmental biodiversity in the surroundings of the study subjects' homes influenced the composition of the bacterial classes on their skin. Compared with healthy individuals, atopic individuals had lower environmental biodiversity in the surroundings of their homes and significantly lower generic diversity of gammaproteobacteria on their skin. The functional role of the gram-negative gammaproteobacteria is supported by in vitro measurements of expression of IL-10, a key anti-inflammatory cytokine in immunologic tolerance, in peripheral blood mononuclear cells. In healthy, but not in atopic, individuals, IL-10 expression was positively correlated with the abundance of the gammaproteobacterial genus Acinetobacter on the skin. These results raise fundamental questions about the consequences of biodiversity loss for both allergic conditions and public health in general.
authors.affiliation: Department of Biosciences, University of Helsinki, FI-00014 Helsinki, Finland. ilkka.hanski@helsinki.fi
authors.forename: Ilkka
authors.initials: I
authors.lastname: Hanski
authors.forename: Leena
authors.initials: L
authors.lastname: von Hertzen
authors.forename: Nanna
authors.initials: N
authors.lastname: Fyhrquist
authors.forename: Kaisa
authors.initials: K
authors.lastname: Koskinen
authors.forename: Kaisa
authors.initials: K
authors.lastname: Torppa
authors.forename: Tiina
authors.initials: T
authors.lastname: Laatikainen
authors.forename: Piia
authors.initials: P
authors.lastname: Karisola
authors.forename: Petri
authors.initials: P
authors.lastname: Auvinen
authors.forename: Lars
authors.initials: L
authors.lastname: Paulin
authors.forename: Mika J
authors.initials: MJ
authors.lastname: Mäkelä
authors.forename: Erkki
authors.initials: E
authors.lastname: Vartiainen
authors.forename: Timo U
authors.initials: TU
authors.lastname: Kosunen
authors.forename: Harri
authors.initials: H
authors.lastname: Alenius
authors.forename: Tari
authors.initials: T
authors.lastname: Haahtela
mesh_terms: D000150:Acinetobacter / Q000276:immunology; D000293:Adolescent; D020561:Alphaproteobacteria / Q000276:immunology; D001407:Bacillus / Q000276:immunology; D020562:Betaproteobacteria / Q000276:immunology; D044822:Biodiversity; D002962:Civilization; D003013:Clostridium / Q000276:immunology; D004781:Environmental Exposure; D005387:Finland / Q000453:epidemiology; D020563:Gammaproteobacteria / Q000276:immunology; D006801:Humans; D061148:Hygiene Hypothesis; D006967:Hypersensitivity / Q000453:epidemiology / Q000276:immunology* / Q000382:microbiology*; D016015:Logistic Models; D054892:Metagenome / Q000276:immunology*; D015995:Prevalence; D011897:Random Allocation; D012867:Skin / Q000276:immunology / Q000382:microbiology