Intratracheal instillation of an anti-TNF neutralizing antibody into the lungs 5 min before bacterial instillation is shown to prevent the increase in AFC in rats with pneumonia (Rezaiguia et al., 1997) and instillation of 5 mg TNF in normal rats increased AFC by 43% over 1h compared to control rats receiving vehicle (Rezaiguia et al., 1997), an effect not blunted by propranolol. Here, TNF is linked to susceptibility to pneumonia measurement.