Growing up on a farm directly affects the regulation of the immune system and causes a reduction in the immunological responses to food proteins, according to a new study led by Bristol veterinary school.
Immunological diseases, such as eczema and asthma, are on the increase in westernised society and represent a major challenge for 21st century medicine.
Now, a study undertaken by Bristol Veterinary School has proved, for the first time, that growing up on a farm directly affects the regulation of the immune system and causes a reduction in the immunological responses to food proteins.
Previous epidemiological studies have suggested a link between growing up on a farm and a reduced likelihood of developing allergic disease but, until now, it has been impossible to demonstrate “direct cause and effect”.
However, researchers at Bristol have discovered that spending early life in a complex farm environment increases the number of regulatory T-lymphocytes – cells that damp down the immune system and limit immune responses.
Led by Marie Lewis, research associate in infection and immunity at the University of Bristol’s School of Veterinary Sciences, the study compared piglets nursed by their mothers on a farm with siblings kept in an isolator unit under very hygienic conditions and fed formula milk (to reflect the environment human babies are raised in).
The work was carried out in piglets as they are valuable translational models for humans since they share many aspects of physiology, metabolism, genetics and immunity.
Compared to their brothers and sisters in the isolator, the farm-reared piglets had reduced overall numbers of T-lymphocytes (the immune cells which drive immune responses) in their intestinal tissues, but significantly increased numbers of a subset of these cells, the regulatory T-lymphocytes, which pacify immune responses and limit inflammation.
Regulatory T-cells have been identified in many mammalian species, including humans, and appear to be universal regulators of immune systems and a reduction in their numbers is often associated with the development of allergies, autoimmune and inflammatory diseases.
Dr Lewis said: “At this point it is not clear exactly what caused the increased capacity for immune regulation in our farm-reared piglets. Our previous work suggests that intestinal bacteria play a pivotal role in the development of a competent immune system and these bacteria are obtained from the environment during early life.”
Additional work is required to determine the extent to which other farm-associated factors contributed to the impact of the environment on increased local and systemic immune regulation. These include:
- Social and maternal interactions,
- Aerial contaminants,
- Antigens from bedding, and
- Early nutrition.
Further clarification of the mechanisms underlying these interactions could lead to methods of intervention during infancy to prevent the development of immune diseases in later life.
- Paper: Direct experimental evidence that early-life farm environment influences regulation of immune responses, Marie C. Lewis, Charlotte F. Inman, Dilip Patel, Bettina Schmidt, Imke Mulder, Bevis Miller, Bhupinder P. Gill, John Pluske, Denise Kelly, Christopher R. Stokes & Michael Bailey, Pediatric Allergy and Immunology, February 3, 2012.
Clean piglets ©iStockphoto.com/MaXPdia