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Proc Natl Acad Sci U S A. 2018 May 15;115(20):5259-5264. doi: 10.1073/pnas.1719866115. Epub 2018 Apr 30.

Less immune activation following social stress in rural vs. urban participants raised with regular or no animal contact, respectively.

Author information

1
Laboratory for Molecular Psychosomatics, Clinic for Psychosomatic Medicine and Psychotherapy, Ulm University, 89081 Ulm, Germany.
2
Clinic for Psychosomatic Medicine and Psychotherapy, Ulm University, 89081 Ulm, Germany.
3
Chair of Health Psychology, Department of Psychology, Friedrich Alexander University, Erlangen-Nürnberg, 91054 Erlangen, Germany.
4
Center for Clinical Microbiology, University College London (UCL), WC1E 6BT London, United Kingdom.
5
Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309.
6
Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309.
7
Department of Physical Medicine & Rehabilitation, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.
8
Center for Neuroscience, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.
9
Rocky Mountain Mental Illness Research Education and Clinical Center (MIRECC), Denver, CO 80220.
10
Military and Veteran Microbiome Consortium for Research and Education (MVM-CoRE), Denver Veterans Affairs Medical Center (VAMC), Denver, CO 80220.
11
Laboratory for Molecular Psychosomatics, Clinic for Psychosomatic Medicine and Psychotherapy, Ulm University, 89081 Ulm, Germany; stefan.reber@uniklinik-ulm.de.

Abstract

Urbanization is on the rise, and environments offering a narrow range of microbial exposures are linked to an increased prevalence of both physical and mental disorders. Human and animal studies suggest that an overreactive immune system not only accompanies stress-associated disorders but might even be causally involved in their pathogenesis. Here, we show in young [mean age, years (SD): rural, 25.1 (0.78); urban, 24.5 (0.88)] healthy human volunteers that urban upbringing in the absence of pets (n = 20), relative to rural upbringing in the presence of farm animals (n = 20), was associated with a more pronounced increase in the number of peripheral blood mononuclear cells (PBMCs) and plasma interleukin 6 (IL-6) concentrations following acute psychosocial stress induced by the Trier social stress test (TSST). Moreover, ex vivo-cultured PBMCs from urban participants raised in the absence of animals secreted more IL-6 in response to the T cell-specific mitogen Con A. In turn, antiinflammatory IL-10 secretion was suppressed following TSST in urban participants raised in the absence of animals, suggesting immunoregulatory deficits, relative to rural participants raised in the presence of animals. Questionnaires, plasma cortisol, and salivary α-amylase, however, indicated the experimental protocol was more stressful and anxiogenic for rural participants raised in the presence of animals. Together, our findings support the hypothesis that urban vs. rural upbringing in the absence or presence of animals, respectively, increases vulnerability to stress-associated physical and mental disorders by compromising adequate resolution of systemic immune activation following social stress and, in turn, aggravating stress-associated systemic immune activation.

KEYWORDS:

TSST; inflammation; old friends; rural; urban

PMID:
29712842
PMCID:
PMC5960295
DOI:
10.1073/pnas.1719866115
[Indexed for MEDLINE]
Free PMC Article

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