Inhalation of PM2.5 does not modulate host defense or immune parameters inblood or lung of normal human subjects

We tested the hypothesis that exposure of healthy volunteers to concentrate d ambient air particles (CAPS) between 0.1 and 2.5 mum in diameter is assoc iated with modulation of human alveolar macrophage (AM) function, cytokine production, and immune phenotype in both blood and lung. Thirty-eight volun teers were exposed to either filtered air or CAPS from the immediate enviro nment of the U.S. Environmental Protection Agency human studies facility in Chapel Hill, North Carolina, USA. Particle concentrations in the chamber d uring the exposures ranged from 23.1 to 311.1 mug/m(3). No symptoms were no ted by volunteers after the exposure. Eighteen hours after exposure, analys is of cells obtained by bronchoalveolar lavage (BAL) showed a mild increase in neutrophils in both the bronchial (8.4 +/- 2%) and alveolar fractions ( 4.2 +/- 1.7%) in subjects exposed to the highest concentration of CAPS comp ared to neutrophils in the fluids of those exposed to filtered air (bronchi al fraction 2.7 +/- 0.6 %; alveolar fraction 0.8 +/- 0.3%). There was no ch ange in the percentage of lymphocytes or AMs recovered in the lavage after inhalation of the highest particle levels (mean 207 mug/m(3)). There was al so no change in the proportion of lymphocytes in the BAL expressing CD3, CD 4, CD8, CD19, nor activation markers CD25 or CD69. Particle inhalation did not affect the expression of CD11 b, CD64, CD16, CD14, CD71 on AM, nor was there an effect on phagocytosis or oxidant generation following stimulation with zymosan A. IL-6 and IL-8 levels detected by enzyme-linked immunoabsor bent assay in the BAL were unrelated to inhaled particle levels. The distri bution of lymphocyte subsets in blood obtained 18 hr after exposure to CAPS did not differ from that found before exposure. We conclude that ambient a ir particles are capable of inducing a mild inflammation in the lower respi ratory tract but have no effect on immune phenotype or macrophage function under the conditions tested.