Treatment with dexamethasone prior to secondary live virus infection prevents airway hyperreactivity only in sensitized animals.

<p>Some animals were treated with dexamethasone (i.p.) before the second live PIV infection. <b>(A)</b> Dexamethasone treatment of non-sensitized animals before secondary infection with PIV (n = 6) had no effect on bronchoconstriction in response to histamine (i.v.), compared to untreated animals (n = 5). In contrast, in OVA-sensitized animals, dexamethasone treatment (n = 3) significantly reduced bronchoconstriction responses (n = 4; p = 0.001). Sham inoculated controls were also included (n = 5 each). <b>(B)</b> Dexamethasone treatment before live PIV re-infection (white bars, n = 4, p<0.01) induced a significant decrease in total cell numbers compared to untreated and re-infected non-sensitized and sensitized animals (n = 6: p<0.01), but this did not reach statistical significance for individual cell counts. Error bars represent SEM.