Different immunomodulatory effects associated with sub-micrometer particles in ambient air from rural, urban and industrial areas

Immunomodulatory effects of chemicals adsorbed to particles with aerodynamic diameter below 0.49 μm (PM0.5) collected in winter 2001 at three sampling points (industrial area [LPIn], traffic-influenced urban area [LPCi], and control area [LPCo]) of La Plata, Argentina, were investigated. The sampling of particulate matter was carried out with high-volume collectors using cascade impactors. PM0.5-adsorbed compounds were hexane-extracted by accelerated solvent extraction. For immunological investigations, human peripheral blood lymphocytes were activated by phytohemagglutinin and exposed to dimethyl-sulfoxide dilutions of PM0.5-extracts for 24 h. Vitality/proliferation was quantified using MTT, released interferon-γ (IFN-γ) and interleukin-4 (IL-4) by ELISA. Cytokine production but not vitality/proliferation was significantly suppressed by all of the highest extract concentrations. Generally, suppression of IFN-γ by PM0.5-extracts was stronger than those of IL-4. Based on administered mass of PM0.5, all extracts suppressed IFN-γ production nearly uniform. Contrary, LPCi-extracts exerted maximum IFN-γ suppression based either on air volume or regarding PM0.5-adsorbed PAH. Also the ranking of PM0.5-associated effects on IL-4 production differs in dependence of the chosen reference points, either mass or [μg/ml] or air volume [m3/ml] related dust quantities in cell culture. Based on the corresponding air volume, LPCi-extracts inhibited IL-4 production to the maximum extend, whereas suppression of IL-4 was comparable based on concentrations. This indicates that not only the disparate PM0.5-masses in air cause varying impacts, but also that disparities in PM0.5-adsorbed chemicals provoke different effects on immune responses and shifts in the regulatory balance that might have implications for allergy and cancer development.