Studies have shown that early exposure to farm animals reduces the risk of children developing atopic diseases, but scientists are still investigating the specific interactions between the immune system and a person’s environment that cause this effect. Scientists from the University of Eastern Finland offer their results as a piece of the puzzle. Their recently published study in the Scandinavian Journal of Immunology and Clinical Experiment Allergy
examined the immunological differences between both farm and non-farm exposed children and between farm and pet exposure.
Asthma, allergic rhinitis, and atopic dermatitis are all atopic diseases for which children growing up on farms have been shown to have reduced risk (Current Opinion in Pediatrics
). All of these conditions are mediated by immunoglobulin E (IgE) and are “frequently present together in the same individual and family (COP
). To investigate the connection between IgE, farm exposure in young children, and an enhanced immune system, Heidi Kaario, MSc, compared children with exposure to children without farm exposure.
Dendritic cells warn T lymphocytes of antigen presence, the first step of mounting a specific immune response. In the words of Ralph Steinman, PhD, from The Rockefeller University
, dendritic cells are “the interfaces between our bodies and the environment. Steinman was the first scientist to identify dendritic cells in 1973. Because of their connection to the environment, Kaario looked at the difference of impact on dendritic cells and cytokine production between the two groups of children.
To test the response of the immune system, Kaario and her team stimulated the study participants with lipopolysaccharide (LPS), an endotoxin found in the membrane of Gram-negative bacteria that prompts a strong immune response in humans (Journal of Endotoxin Research
). The children with farm exposure showed a lower percentage of dendritic cells responding to the LPS stimulation than the non-farm children. In addition, more non-allergenic Th1-associated cells and regulatory cytokines were produced in farm children stimulated with LPS. These results indicated the immune systems of farm-exposed children had the capability to activate “tolerogenic immune mechanisms,” meaning they are capable of producing immunological tolerance (Merriam Webster Medical Dictionary
Additionally, Karrio observed that “an increase in the number of specific farm exposures (consumption of farm milk, exposures to stables and hay barns) was dose-dependently associated with lower lipopolysaccharide-induced production of proinflammatory cytokine TNF,” providing further evidence for the impact of farm exposure on children’s’ immune systems.
In a further study comparing exposure to house pets like cats and dogs to farm exposure, contact with pets by young children did also prove to have an “immunomodulatory” impact, but in a different way than in farm children.
In future studies, this group plans to identify what exactly in the farm environment is providing young children with the ability to resist risk to atopic diseases.
To learn more about dendritic cells as "antigen-presenting cells," check out the following video: