Effect of serial-day exposure to nitrogen dioxide on airway and blood leukocytes and lymphocyte subsets

Nitrogen dioxide NO2) is a free radical-producing oxidant gas. Inhalation o f NO2 could cause airway inflammation, and decrease immune function. This e xperiment tested the hypothesis that exposure to NO2 would: 1) increase leu kocytes in bronchoalveolar lavage (BAL); and 2) change the distribution of lymphocyte subsets and activation in BAL and peripheral blood (PB). Using a counter-balanced, repeated-measures design, 15 healthy volunteers w ere exposed to filtered air (FA) or 2.0 parts per million NO2 for 4 h.day(- 1) (4 x 30 min of exercise), for three consecutive days. Bronchoscopy was p erformed 18 h following each exposure set, and PB was drawn pre-exposure an d pre-bronchoscopy. Flow cytometry was used to enumerate lymphocyte subsets and activation makers in BAL and PB. In the bronchial fraction, there was an increase in the percentage of neutr ophils following NO2 exposure compared to FA (median (interquartile range): 10.6 (4.8. 17.2)% versus 5.3 (2.5-8.3)%; p=0.005). In the BAL, there was a decrease in the percentage of T-helper cells following NO2 exposure compar ed to FA (55.9 (40.8-62.7)% versus 61.6 (52.6-65.2)%; p=0.022). For PB, the re were no between-condition differences in any leukocyte or lymphocyte sub sets, or activation. In conclusion exposure to nitrogen dioxide results in bronchial inflammatio n and a minimal change in bronchoalveolar lavage T-helper cells, and no cha nges in peripheral blood cells.