Kinetics of inflammatory cytokines in the clearance of non-typeable Haemophilus influenzae from the lung

Levels of the pro-inflammatory cytokines TNF-alpha and IFN-gamma were measu red from the time of infection to the time of complete clearance of non-typ eable Haemophilus influenzae (NTHi) from the lung in immune and non-immune rats. Mucosal immunization facilitated production of significant levels of TNF-alpha as early as 30 min post-pulmonary challenge with NTHi in immune a nimals. Following the peak at 2 h, rapid decline of TNF-alpha levels occurr ed from the alveolar spaces. Levels of TNF-alpha in non-immunized animals i ncreased at a slower rate, peaked at a lower concentration and were slower to decline. The significantly larger number of macrophages seen in the immu ne animals at I h after bacterial challenge could partially account for the higher levels of TNF-alpha. Interferon-gamma was not detected in immune or non-immune rats at any time point before NTHi clearance after pulmonary ch allenge. Study of the kinetics of TNF-alpha release demonstrates that immun ized animals control the release of pro-inflammatory cytokines more effecti vely than non-immunized animals for enhanced clearance of bacterial infecti on from the lungs.