Adjuvant activity of particulate pollutants in different mouse models.

Particulate air pollutants may play a role in the increasing prevalence of respiratory allergy by acting as adjuvants for a T helper 2 (Th2) mediated immune response to common allergens. The immunomodulating capacity of well-defined polystyrene particles as well as different particles as present in our environment (diesel exhaust, carbon black, and silica particles) was investigated in different models. Polystyrene particles were injected intraperitoneally or installed intratracheally, while the environmentally relevant particles were injected subcutaneously. From these studies, it becomes clear that all particles exert an adjuvant effect on the immune response to the co-administered antigen. The particle core rather than attached chemical factors seems to be mainly responsible for this effect. The different particles, however, stimulate different types of immune responses, indicating that physicochemical properties of particles may be of importance in steering the response towards a T helper 1 (Th1) or a Th2-like response.