A study published in Pediatric Allergy and Immunology examined how white blood cells respond to air from different environments to better understand allergic disease.
As the world becomes more urban, we are exposed to more and more pollutants in the environment. Pollutants in the air contribute to the incidence of cardiovascular disease, and allergic diseases, including asthma, and allergies. Although individuals raised rural environments have lower incidences of asthma and allergies, air pollution is the greatest environmental risk worldwide and was found to affect 92% of the population.
Low rates of allergic disease among those raised in rural environments
The low rates of allergic disease among individuals raised in rural environments implies different environments stimulate immune responses in different ways. In a study published in Pediatric Allergy and Immunology researchers analyzed the effects of different environments on the immune system.
The study population consisted of 18, 4-year-old children from Finland, 11 of which were boys and six of which had a predisposition for allergies. None of the children grew up in a rural environment or an environment with excessive air pollution. Researchers studied the expression of peripheral blood mononuclear cells, which include monocytes, lymphocytes and macrophages, in response to different air particles. After the children’s blood samples were taken, the mononuclear cells were exposed to farm dust or urban particulate matter.
Farm dust causes an increase in immune response
Exposure to farm dust resulted in more cells expressing cytokines, CD80 receptors, which are implicated in immune responses, and reduced the expression of ILT4 receptor, which inhibits immune responses. Conversely, particulate matter from urban air caused lower expression of CD80 receptors and ILT4 receptors. After sampling the components of both air types, farm dust did not consist of illness-inducing Polycyclic Aromatic Hydrocarbon compounds.
The decrease in immune response with urban particulate matter counters previous research in mice that suggests the immune response increases. Although the exact pathway is unclear, this inhibitory immune response likely signals the body to tolerate the particular matter, interfering with normal immune regulation which makes the individual more prone to allergic disease.
To better understand the relationship between urban particulate matter, rural air and allergic disease, future research should choose a larger sample size of children as well as take samples of air from different urban and rural areas.
Written by Monica Naatey-Ahumah, BSc
Reference: Martikainen, M.V., Rönkkö, T.J., Schaub, B., Täubel, M., Gu, C., Wong, G.,…Roponen, M. (2018).  Integrating farm and air pollution studies in search for immunoregulatory mechanisms operating in protective and high- risk environments. Pediatric Allergy and Immunnology, 29, 815-822. https://doi.org/10.1111/pai.12975
