The many faces of the hygiene hypothesis

Schaub, Bianca; Lauener, Roger; Mutius, Erika von

doi:10.1016/j.jaci.2006.03.003

Cited by 344 publications

(235 citation statements)

References 117 publications

(113 reference statements)

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“…Prevalence, as estimated in the 2007 NHIS, remains at historically high levels. That is, 9.1% of children (6.7 million) were estimated to have asthma currently, 5.2% of children (3.8 million), or nearly 60% of children with current asthma, had experienced Ն1 asthma attack in the previous year, and 13.1% of children (9.6 million) had been diagnosed as having asthma during their lifetimes. Of this group, 70% were reported to have asthma currently.…”

Section: Asthma Prevalence Among Children Remains Highmentioning

confidence: 99%

Status of Childhood Asthma in the United States, 1980–2007

et al. 2009

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Centers for Disease Control and Prevention data were used to describe 1980 -2007 trends among children 0 to 17 years of age and recent patterns according to gender, race, and age. Asthma period prevalence increased by 4.6% per year from 1980 to 1996. New measures introduced in 1997 show a plateau at historically high levels; 9.1% of US children (6.7 million) currently had asthma in 2007. Ambulatory care visit rates fluctuated during the 1990s, whereas emergency department visits and hospitalization rates decreased slightly. Asthma-related death rates increased through the middle 1990s but decreased after 1999. Recent data showed higher prevalence among older children (11-17 years), but the highest rates of asthmarelated health care use were among the youngest children (0 -4 years). After controlling for racial differences in prevalence, disparities in adverse outcomes remained; among children with asthma, non-Hispanic black children had greater risks for emergency department visits and death, compared with non-Hispanic white children. For hospitalizations, for which Hispanic ethnicity data were not available, black children had greater risk than white children. However, nonemergency ambulatory care use was lower for non-Hispanic black children. Although the large increases in childhood asthma prevalence have abated, the burden remains large. Potentially avoidable adverse outcomes and racial disparities continue to present challenges. These findings suggest the need for sustained asthma prevention and control efforts for children. Pediatrics 2009;123:S131-S145

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Section: Asthma Prevalence Among Children Remains Highmentioning

confidence: 99%

Status of Childhood Asthma in the United States, 1980–2007

et al. 2009

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“…The 'hygiene hypothesis' suggests that exposure to microbial infections or microbial products may inhibit the development or pathogenesis of allergic responses, including asthma. [1][2][3][4][5] Many epidemiological observations related to various infections support this provocative hypothesis. [6][7][8][9][10][11][12][13][14] In particular, a series of studies have described children who had close contact with farm animals and exhibited significantly lower levels of allergy and asthma later in life.…”

Section: Introductionmentioning

confidence: 99%

Role of dendritic cells: a step forward for the hygiene hypothesis

Yang

Gao

2010

Cell Mol Immunol

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The hygiene hypothesis was proposed more than two decades ago, but its mechanism remains unclear. This review focuses on recent advances in the field, especially on the role played by dendritic cells (DCs) and their modulating effects on various infections and allergic diseases, including allergic asthma. DCs isolated from mice long after the resolution of an infection were reported to have a significant modulating effect on allergen-specific Th2 responses in both in vitro and in vivo systems. These DCs showed DC1-like and/or tolerogenic DC capacity, which allowed for the inhibition of allergic responses by immune deviation (enhancing Th1 response) and immune regulation (through regulatory T-cell and Th2 hyporesponsiveness) mechanisms. These findings represented a significant advance in the elucidation of the mechanisms underlying the hygiene hypothesis. Further investigation on the mechanisms by which DCs are 'educated' by infectious agents and the influence of the type, time, and extent of infections on this 'education' process will help us understand immune regulation in disease settings and in the rational design of preventive/therapeutic approaches to allergy/asthma and infections.

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“…Specifically, it has been hypothesized that exposure to microbial products during early childhood may have an inhibitory effect on the development of allergic diseases [4][5][6]. Notably, in a series of well-performed epidemiological studies on children of European farmers (Allergy and Endotoxin), it was demonstrated that children who grew up in a farming environment and had close contact with farm animals exhibited significantly low levels of allergy and asthma in later life [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Imprinted DC mediate the immune‐educating effect of early‐life microbial exposure

et al. 2009

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It has been long proposed that exposure to environmental factors early in life may have an educating effect on the development of immune regulatory functions. However, experimental studies on this issue are limited and the related molecular and cellular basis remains unclear. Here we report that neonatal exposure to killed bacteria (Chlamydia muridarum, originally called Chlamydia trachomatis mouse pneumonitis (MoPn)) changed the pattern of the hosts' immune responses to a model allergen (OVA) in adulthood. This was associated with altered phenotype and function of DC. We found that DC from adult mice treated neonatally with UV-killed MoPn exhibited distinct patterns of surface marker and TLR expression and cytokine production from control mice (DC from adult mice neonatally treated with vehicle, (Sham-DC)). More importantly, DC from adult mice treated neonatally with UV-killed MoPn induced significantly lower type-2 antigen-specific T-cell responses than Sham-DC shown in DC:T co-culture experiments in vitro and in adoptive transfer experiments in vivo. In addition, depletion of T cells in vivo largely abolished the phenotypic and functional alterations of DC caused by bacterial exposure, suggesting the involvement of T cell in this process. Our study demonstrates a central role of DC in linking the early-life exposure to microbial products and the balanced development of immune regulatory functions and the involvement of T cells in imprinting of the DC function.Key words: Allergy . DC . Hygiene hypothesis . IL-10 . TLR IntroductionThe immune system of a host experiences multiple influences from the outside world during development from birth to adult life. Numerous studies have demonstrated that environmental factors encountered during the developmental stage have considerable effect in shaping the pattern of immune responses in adult life. Therefore, the exposure to ''proper'' environmental antigens in early life might be important for the formation and maintenance of a balanced immune regulatory system in the host, thus preventing autoimmunity and allergic diseases [1,2].Over the past decades, the general burden of infections in the developed areas of the world has been reduced due to a better hygiene, and the ''hygiene hypothesis'' has been raised to explain the significant increase of allergic diseases [3,4]. Specifically, it has been hypothesized that exposure to microbial products during early childhood may have an inhibitory effect on the development of allergic diseases [4][5][6]. Notably, in a series of well-performed epidemiological studies on children of European farmers (Allergy and Endotoxin), it was demonstrated that children who grew up in a farming environment and had close contact with farm animals exhibited significantly low levels of allergy and asthma in later life [7][8][9]. However, the proposed educating effect of exposure to various microbial products during early life on the development of immune regulatory function has not been tested in detail using experimental approaches. 469More i...

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The many faces of the hygiene hypothesis

Cited by 344 publications

References 117 publications

Status of Childhood Asthma in the United States, 1980–2007

Status of Childhood Asthma in the United States, 1980–2007

Role of dendritic cells: a step forward for the hygiene hypothesis

Imprinted DC mediate the immune‐educating effect of early‐life microbial exposure

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