The cytokines IL-1β and TNF-α were measured at days 1, 14, 28 and 56 after infection. Both of these proinflammatory mediators were found to be modestly but significantly elevated (relative to day 1) at days 14 and 56 (P < 0.0001) following aerosol infection, although at much lower levels than is typically observed in the lungs. At day 28, TNF-α levels were only slightly elevated (P = 0.003), and no change was observed for IL-1β (P = 0.6). Three animals were used for cytokine analysis at each time point.