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Schematic overview of the hygiene/''old friends'' hypothesis. Several microbial signals, such as environmental exposure (rural/farm environment) and an archaic microbiota (containing more diverse and abundant bacteria and typical helminth parasites), provide strong signals to develop regulatory responses (tolerance), whereas an urbanized environment and/or a westernized microbiota does not, tipping the immune balance more toward inflammation. Tolerance leads to good health, whereas in its absence, an inflammatory profile leads to airway diseases, such as respiratory allergies and asthma. Composition and diversity of the microbiota are affected by diet. Viral infections, sinusitis, and air pollution trigger the immune system to move toward inflammation, whereas a diverse microbiota might reduce these inflammatory signals.  

Schematic overview of the hygiene/''old friends'' hypothesis. Several microbial signals, such as environmental exposure (rural/farm environment) and an archaic microbiota (containing more diverse and abundant bacteria and typical helminth parasites), provide strong signals to develop regulatory responses (tolerance), whereas an urbanized environment and/or a westernized microbiota does not, tipping the immune balance more toward inflammation. Tolerance leads to good health, whereas in its absence, an inflammatory profile leads to airway diseases, such as respiratory allergies and asthma. Composition and diversity of the microbiota are affected by diet. Viral infections, sinusitis, and air pollution trigger the immune system to move toward inflammation, whereas a diverse microbiota might reduce these inflammatory signals.  

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The worldwide incidence and prevalence of asthma continues to increase. Asthma is now understood as an umbrella term for different phenotypes or endotypes, which arise through different pathophysiologic pathways. Understanding the many factors contributing to development of the disease is important for the identification of novel therapeutic target...

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... the last years, interactions of microbes, including worm parasites, with their host have been identified: exposure to microorganisms not only triggers but also effectively suppresses immune responses, and beneficial effects of microorganisms are increasingly recognized and mechanistically understood. Strate- gies are emerging to potentially implement these effects in novel interventions to prevent or treat allergic diseases, such as allergic asthma (Fig 1). A better understanding of the disease in its many guises at a basic level is needed to endorse such strategies and improve and refine interventions. ...
Context 2
... hypothesis has its origins in observations published in 1989 by Strachan, 5 who noted that decreasing family size was associated with hay fever in developed countries and suggested that this might be related to a lower degree of sibling-related childhood infections and mi- crobial exposure. In extension of the hygiene hypothesis, Rook 6 has postulated the ''old friends'' hypothesis, in which many infec- tious agents and microbes in their coevolution with human sub- jects have developed mechanisms to modulate and evade the host immune system (Fig 1). Immunomodulatory microorgan- isms have been described to activate various cells of the regulato- ry network, such as regulatory T (Treg) cells and regulatory B cells, and to modulate or even reprogram certain antigen- presenting cells, leading to tolerogenic dendritic cells (DCs), alternatively activated macrophages, or both. ...

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... This pathology usually develops after the onset of bronchial asthma (BA) or cystic fibrosis [1] and prevalence rates of ABPA among adult asthmatic patients have been estimated as 2.5% in China and 7-22% in India [2]. Rates differ among countries but appear to be increasing around the world with the increase of BA [3]. Several diagnostic criteria for ABPA have been proposed, such as a history of BA or cystic fibrosis, characteristic radiographic pulmonary opacities including central dilatation of the bronchus, elevated immunoglobulin (Ig)E levels, and hypersensitivity reaction to Aspergillus including elevated IgE antibodies against Aspergillus fumigatus and/or IgG antibodies for Aspergillus [2,4]. ...
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