Flow cytometric analysis of lymphocyte subpopulations in bronchoalveolar lavage fluid after repeated ozone exposure

As known from studies in animal and human subjects, ozone can exert effects on the immune response including allergic sensitisation and allergen respo nsiveness. The objective of the present study was to assess the changes in lymphocyte subsets in bronchoalveolar lavage fluid (BALF) after single and repeated ozone exposures. Twenty-three healthy subjects underwent single ex posures to 200 ppb ozone or filtered air (FA), as well as repeated exposure s to 200 ppb ozone on four consecutive days, each during 4 h of intermitten t exercise. Bronchoalveolar lavage was performed 20 h after the single expo sure or the last of the repeated exposures. Lymphocytes were identified by sideward scatter and CD45 expression, and their subsets by eight different panels of antibodies. Checksums were calculated to assess the validity of t he results. The percentage and the absolute number of lymphocytes, mostly c omprising T-lymphocytes (CD2(+); overall mean 98.8%), increased after singl e (P < 0.05; each), but not after repeated ozone exposure, compared with FA (7.4 vs 5.8 vs 6.5%; 680 vs 419 vs 301 x 10(3)). In addition, we observed small but statistically significant changes in the proportions of lymphocyt e subpopulations. The percentage of CD4(+) lymphocytes increased after sing le (P < 0.05) and repeated ozone exposure (P < 0.01): whereas the percentag e of CD8(+) cells decreased after repeated exposure (P < 0.05). The proport ion of activated lymphocytes (CD25(+)) was elevated after repeated, compare d with single, ozone exposure (P < 0.01), and the percentages of natural ki ller (NK) cells were decreased after both single (P < 0.05) and repealed (P < 0.01) exposures. Our data suggest that single but not repeated ozone exp osures cause a change in absolute numbers of lymphocytes in BALE, whereas t he proportions of lymphocyte subsets are affected by single as well as repe ated exposures.