- Wonderful new paper on Microbial Biodiversity page
shows induction of immmunoregulatory mechanisms
- A 2020 Evolution item, Interviews page
- Updated text, Old Friends & Psychiatry pages
- SARS-CoV-2 on Microbial biodiversity page
- New entries on books page
The Old Friends Hypothesis
What is the relationship between this and the "Biodiversity" and "Hygiene" hypotheses?
Old Friends
Biodiversity
Hygiene
CONTENTS
Click below to see brief descriptions of the other pages
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Old Friends
The pages first describe the "Old Friends" hypothesis, and why this Darwinian concept usefully expands and corrects the original hygiene hypothesis, and increases its explanatory power in several clinical domains. The links between microbial exposures and socioeconomic status are also considered.
The bottom line is that the immune system needs "data" in early life in order to function correctly. Without appropriate microbial inputs the regulation of the immune system is faulty, and the risk of chronic inflammatory disorders increases.
It is becoming clear that the modern deficit in microbial exposures is not primarily a consequence of hygiene in the home, which remains essential to human health. The causes of the reduced exposures are antibiotics, lifestyle changes that limit transmission of maternal microbiota to the infant, or that limit exposure to the microbiota of the natural environment, and unvaried diets. Interestingly, evidence for the role of the natural environment is increasing particularly fast. -
Psychiatry
Enter description here.
This page deals with the implications of faulty immunoregulation for psychiatry, and in particular for depression and reduced stress resilience. If regulation of the immune system is impaired, then a given level of stress will cause abnormally high and persistent levels of systemic inflammation. This persistent inflammation drives malfunctions in the central nervous system that are manifested as certain forms of depression. There is now mounting evidence that such forms of depression can be ameliorated by anti-inflammatory treatments.
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Green Space
Enter description here.
Exposure to green spaces improves physical and psychological health. The Old Friends hypothesis provides a mechanism that can be documented by physiological measures that relate directly to the disorders from which green spaces protect us.
We do not doubt that there is a psychological component, analogous to "habitat selection" in other species, that drives wellbeing and relaxation when we are exposed to green spaces. But just as important, and now readily proven, our immune systems have evolved to require inputs from the microbial biodiversity of the natural environment. This issue is also considered in the microbial biodiversity page. -
Microbial biodiversity
Exposure to microbial biodiversity, especially in the perinatal period (pregnancy and early life) is essential for the developmental and epigenetic establishment of the immune system, endocrine system and metabolism. There appears to be a "window of opportunity" in early life when crucial adjustments are made to these systems, that have life-long effects.
Microbial biodiversity provides data in the form of molecular signals (for example, in the airways), molecular structures (for repertoire development), and organisms for the symbiotic microbiota.
Although the perinatal period is the most critical, it is clear that we also need microbial biodiversity in the gut microbiota in adulthood, and a decline in biodiversity in old age correlates with increasing levels of inflammation, and declining health. -
Interviews
Radio or television interviews on the topic of the "Old Friends Hypothesis" and its clinical implications. Where available the interviews can be played in the page, or accessed via a link provided.
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Recent Lectures
Details of recent lectures that seem particularly significant. Links are given to PDF files of the powerpoint presentation, or to videos, when available.
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Book
Information about books to which I have recently contributed chapters.
Also information about a book on the topic of this website that I edited and partly wrote. This book uses the Old Friends hypothesis as background to a discussion of the increasing prevalences in high-income settings of chronic inflammatory disorders (allergies, autoimmunity, inflammatory bowel disease) and of disorders linked to persistent redundant inflammation (cardiovascular disease, metabolic syndrome, depression, some cancers).
These increases are attributable to a broad defect in immunoregulation in high-income settings, which is at least partly driven by failing microbial inputs to the immune system.
The authors discuss the potential role of failing immunoregulation in the aetiology of chronic inflammatory diseases of the organ systems that are the fields of their specialist expertise.
The book was published in 2009, so parts of it are somewhat dated.
Prof Graham A.W. Rook, BA, MB, BChir, MD.
Centre for Clinical Microbiology
UCL (University College London) email:- g.rook@ucl.ac.uk