Farm exposure as "immunotherapy" against allergic diseases

Maternal farm exposure decreases the risk of allergic disease in the offspring.

Offspring of farming mothers have:

- higher number and more efficient function of regulatory T cells (T-reg cells that express CD4, CD25 and Foxp3)

- lower TH2 cytokine secretion (IL-5) and lymphocyte proliferation


Interleukin 5. Image source: Wikipedia, public domain.

Maternal exposure to an increasing number of farm animals and stables exerts effects on both Treg cells and TH1/TH2 cells.

Even noncontinuous exposure to farm animals has an effect of higher TH1 and increased IFN-gamma secretion.

One speculation is that maternal farm exposure may result in a “natural model of immunotherapy or prophylaxis” protecting the child from developing allergic diseases.

Children living on a farm are at reduced risk of asthma (OR 0.68), hay fever (OR, 0.43), atopic dermatitis (OR, 0.80), and atopic sensitization (OR, 0.54) http://goo.gl/qVY2G

References:

Farm exposure—a novel natural model of immunotherapy against allergic diseases? JACI, Apr 2009.
Maternal farm exposure modulates neonatal immune mechanisms through regulatory T cells. Bianca Schaub et al. JACI, Volume 123, Issue 4, Pages 774-782.e5 (April 2009).
How to reduce your risk of asthma: spend your whole life on a farm
Children living on farms exposed to a wider range of microbes leading to lower asthma risk. NEJM, 2011.
Protective role of contact with livestock and farming lifestyle on asthma, in particular during childhood. ERJ January 1, 2012 vol. 39 no. 1 67-75.
Image source: OpenClipArt.org, public domain.