Ruokolainen L, von Hertzen L, Fyhrquist N, Laatikainen T, Lehtomäki J, Auvinen P, Karvonen A M, Hyvärinen A, Tillmann V, Niemelä O, Knip M, Haahtela T, Pekkanen J, Hanski I
Department of Biosciences, University of Helsinki, Helsinki, Finland.
Allergy. 2015 Feb;70(2):195-202. doi: 10.1111/all.12545.
Western lifestyle is associated with high prevalence of allergy, asthma and other chronic inflammatory disorders. To explain this association, we tested the 'biodiversity hypothesis', which posits that reduced contact of children with environmental biodiversity, including environmental microbiota in natural habitats, has adverse consequences on the assembly of human commensal microbiota and its contribution to immune tolerance.
We analysed four study cohorts from Finland and Estonia (n = 1044) comprising children and adolescents aged 0.5-20 years. The prevalence of atopic sensitization was assessed by measuring serum IgE specific to inhalant allergens. We calculated the proportion of five land-use types--forest, agricultural land, built areas, wetlands and water bodies--in the landscape around the homes using the CORINE2006 classification.
The cover of forest and agricultural land within 2-5 km from the home was inversely and significantly associated with atopic sensitization. This relationship was observed for children 6 years of age and older. Land-use pattern explained 20% of the variation in the relative abundance of Proteobacteria on the skin of healthy individuals, supporting the hypothesis of a strong environmental effect on the commensal microbiota.
The amount of green environment (forest and agricultural land) around homes was inversely associated with the risk of atopic sensitization in children. The results indicate that early-life exposure to green environments is especially important. The environmental effect may be mediated via the effect of environmental microbiota on the commensal microbiota influencing immunotolerance.
西方生活方式与过敏、哮喘及其他慢性炎症性疾病的高患病率相关。为解释这种关联，我们检验了“生物多样性假说”，该假说认为儿童与环境生物多样性（包括自然栖息地中的环境微生物群）的接触减少，会对人类共生微生物群的组装及其对免疫耐受的作用产生不利影响。
我们分析了来自芬兰和爱沙尼亚的四个研究队列（n = 1044），这些队列由0.5 - 20岁的儿童和青少年组成。通过测量针对吸入性过敏原的血清IgE来评估特应性致敏的患病率。我们使用CORINE2006分类法计算了家庭周围景观中五种土地利用类型（森林、农田、建成区、湿地和水体）的比例。
距离家庭2 - 5公里范围内森林和农田的覆盖率与特应性致敏呈显著负相关。6岁及以上儿童中观察到了这种关系。土地利用模式解释了健康个体皮肤中变形菌门相对丰度变化的20%，支持了环境对共生微生物群有强烈影响的假说。
家庭周围绿色环境（森林和农田）的数量与儿童特应性致敏风险呈负相关。结果表明生命早期接触绿色环境尤为重要。环境影响可能是通过环境微生物群对共生微生物群的作用来介导的，进而影响免疫耐受。
