Mechanical ventilation induced exacerbation of pulmonary inflammation in pneumonia independently of leukocyte counts. Pneumococcal pneumonia (S.p.) was induced 24 hours before mechanical ventilation (MV) was performed for 6 hours. Continuous adrenomedullin (AM) infusion (0.05 mg/kg/hour) started with the onset of MV. Nonventilated mice were sacrificed 30 hours after infection. (A) Cytokine levels of interleukin (IL)-1β, IL-6, keratinocyte-derived cytokine (KC) and IL-10 were measured in lung homogenate. **P < 0.01; n = 6 each. (B) Leukocytes were isolated from lung homogenate and differentiated by flow cytometry. **P < 0.01; n = 5 each. PMN, polymorphonuclear neutrophils.