Harnessing immune tolerance in the fight against allergies and asthma

Previously, it was widely believed that avoiding exposure to allergens could prevent the development of allergies. In the light of new research on immune tolerance, the Finnish Allergy Programme revisited allergy management practices. The goal of the programme was established: to promote immunological and psychological resilience, rather than relying on excessive avoidance of allergens. (2) 

The development of immune tolerance is a dynamic and complex process influenced by gene-environment interactions. Typically, infants develop tolerance to common environmental allergens, but in some cases hypersensitivity (i.e. intolerance) can develop instead. One critical factor for normal tolerance development seems to be microbial exposure, particularly to environmental microorganisms and commensals in the normal flora. (2,3)

From allergen immunotherapy to enriching daycare yards

Allergen immunotherapy has been used for over a century to treat allergies by inducing tolerance through repeated exposure to an allergen. (1) Professor Haahtela described the increasing availability of different kinds of immunotherapies as good news and continues: “Combining these therapies with contact with nature is an excellent combination to improve your health and also prevent further disease”.

There is growing evidence that suggests a connection between immune tolerance and nature relatedness. The Karelia Allergy Study investigated the striking contrast in allergy prevalence between the Finnish and Russian Karelia populations. After World War II, Finnish Karelia underwent rapid urbanisation and improvement in living standards, while Russian Karelia continued an agricultural lifestyle. (4)

In 2003, 26.6% of Finnish schoolchildren had a positive skin prick test to birch pollen, compared to only 2% of Russian children (p=0.000). Asthma was also more prevalent in Finnish children, with 8.8% affected compared to only 1.6% in Russian children (p=0.000). (5) The study's findings suggest that the significant differences in lifestyle and environment may have contributed to a richer gene-microbe network in the Russian population, leading to a more balanced innate immunity and a lower prevalence of allergies. (4)

In a controlled intervention study that manipulated the biodiversity of daycare centre yards, enriching them with forest floor and sod, the skin and gut microbiota of children became more diverse. This diversity was associated with an enhancement of immunoregulatory pathways. (6) 

The results support the biodiversity hypothesis, which proposes that exposure to natural environments enhances the diversity of microorganisms in the human body, promoting immune balance and disease protection. (1)

Endorsing tolerance and health instead of avoidance

The Finnish Allergy Programme implemented the biodiversity hypothesis into practice by promoting immune tolerance, contacts with natural environments, and allergy health.

Professor Haahtela encouraged clinicians to broaden their approach to allergy management, advising them to provide guidance on how patients can improve their health by adopting preventive measures in their environment and lifestyle, in addition to medication. The practical guidance endorsed in the Finnish Allergy Programme to promote tolerance is summarised in a figure below. More information on the tactics and results of the Allergy Programme will follow in an upcoming episode!

Figure 1. Practical advice to strengthen immune tolerance in the Finnish Allergy Programme (2008–2018). (3,4)