Particle size and source; effects on allergy adjuvant activity and innate immunity

Abstract

While traffic-related particulate air pollution has been associated with both exacerbation and development of asthma and allergic diseases, little is known about the health effects of wood smoke particles.<br> The purpose of this study was to compare the capacity of wood smoke particles and road traffic particles to increase the development of allergy, by measuring their adjuvant effect on allergen-specific IgE production. To investigate the importance of particles size, road traffic particles with different proportions of ultrafine combustion particles and coarse mineral particles, as well as chemical-free model particles with a similar size range, were tested. We also explored the acute effect of particles on innate immune cell activation, since the innate immune system has increasingly been recognised as an important modifier of adaptive immune responses, including allergic sensitisation.<br> In conclusion, wood smoke particles and mixed road traffic particles had similar capacity to increase the development of allergic disease, although less than diesel exhaust particles. The adjuvant capacity of particles increased with decreasing particle size, and fine combustion particles seemed to be responsible for the adjuvant effects. The effect appeared, however, to be modulated by particle-associated chemicals. Different mechanisms behind the activation of innate immune cells by fine and coarse particles may be important also for their different capacity to increase allergic sensitisation.