In a recent study, published in Clinical & Experimental Allergy by Heidi Kääriö et al., using samples from the Protection Against Allergy-Study in Rural Environments (PASTURE) birth cohort, demonstrate that farm exposures (stables, hay barn, farm milk) at age 4.5 years is linked to amplified Th1-type cytokine production.
There have been recent advances into the understanding of how farming exposures might differentially affect various asthmatic phenotypes. Based upon age and type of farming exposures, a wide range of studies have demonstrated protective or deleterious effects of the farming environment on asthma conditions.
The evidence supporting the theory of farming exposures as variably protective against the development of asthma and in support of the “hygiene hypothesis” is strongest in several European pediatric cohorts.
Potential explanations for the immune-protective effects of these various farming exposures have focused on innate immune signaling pathways, particularly the highly conserved Toll-like receptor (TLR) recognition signaling pathways. In general, activation of TLRs enhance T-helper (Th)1 immune responses as opposed to the allergic, Th2 polarized immune responses. Including the theory that early farm exposure (includingin utero) modulate the innate immune system.
In their study, published in Clinical & Experimental Allergy, Heidi Kääriö et al., the research group from Finland and Germany report that peripheral blood mononuclear cells (PBMCs) from farm children produced more Th1-associated cytokines such as IL-12 and interferon (IFN)-γ, and immunoregulatory cytokines such as IL-10. Interestingly, the number of farm exposures correlated with higher IFN-γ levels.
Children growing up on a farm have significantly less asthma, hay fever and atopic reactions. Farm exposure provides protection from childhood asthma and allergic diseases, but the causal mechanisms remain poorly understood.
It is also known that T helper (Th) 2-type cytokines such as interleukin (IL)-4, IL-5 and IL-13 drive allergic/asthma reactions, whereas Th1-type cytokines antagonize these effects.
Thus, growing up on a farm, in early childhood, and its related Th1-type immune responses may be linked to suppressed, allergy related Th2-type responses, and this may provide help explaining the protection of farming lifestyle on asthma and allergy development in children.
Keping in mind that cowsheds and unprocessed cow’s milk are “soups” containing myriads of potentially relevant elements. Moreover, the diversity of farm animal exposure during pregnancy has been associated with lower risk of atopic dermatitis and higher IFN-y and TNF-α levelsin supernatants of cord blood mononuclear cells stimulated with LPS.
Finally, the diversity of the environmental and human nasal microbiome, respectively, have been associated with lower risk of asthma in the farm populations.