ROLE OF TUMOR-NECROSIS-FACTOR-ALPHA IN INNATE RESISTANCE TO MOUSE PULMONARY INFECTION WITH PSEUDOMONAS-AERUGINOSA

In the present study, we have investigated the mechanisms underlying mouse resistance to endobronchial infection with Pseudomonas aeruginosa enmeshed in agar beads, This was done by monitoring macrophage activation-associated gene expression in lung and alveolar cells harvested from resistant (BALB/c) and susceptible (DBA/2, C57BL/6, and A/J) strains of mice over the course of infection with P, aeruginosa. Interleukin-1 alpha, interleukin-1 beta, macrophage inflammatory protein-1 alpha, JE, and tumor necrosis factor alpha (TNF-alpha) mRNA expression levels were up-regulated in all strains of mice during the early phase of the infection, The level of TNF-alpha mRNA expression was increased to a greater extent in resistant BALB/c mice than in susceptible DBA/2, C57BL/6, and A/J strains of mice, This observation paralleled a higher secretion of TNF-alpha into the alveolar space of BALB/c mice at 3 and 6 h postinfection. The concentration of TNF-alpha released in alveoli returned to basal levels within 24 h of infection in mice of all strains, even though the TNF-alpha mRNA expression remained high until 3 days after infection, In vivo treatments with either anti-murine TNF-alpha monoclonal antibodies or with aminoguanidine significantly increased the number of P, aeruginosa bacteria detected in the lungs of resistant mice at 3 days postinfection, Overall, these findings indicate that both TNF-alpha and nitric oxide exert a protective role in response to pulmonary infection with P. aeruginosa.