TNF and susceptibility to pneumonia measurement: There was an increased early BALF TNF response after infection with the TIGR4 strain compared to infection with the TIGR4 Δcps strains in a model of early pneumonia, with differences persisting when using different inoculum doses, nonreplicating bacteria, and at time points when TIGR4 and TIGR4 Δcps strains showed no significant differences in BALF CFU (e.g., 4 h data after low-dose infection).