Figure 4.

Both bacterial burden and cytokine induction in spleen cells of mice after lethal intravenous or intranasal challenge with L. pneumophila. (A) Each group of mice (n = 6/group) was immunized s.c. with P8 plus CpG-ODN at 0, 1, and 2 weeks. At 3 weeks, the mice were challenged i.v. with L. pneumophila at 2 × 10⁷ CFU per mouse. The mice were sacrificed 48 h post-challenge, the lungs were harvested, and the number of viable bacteria in the lung tissues was determined. (B) Each group of mice (n = 6/group) was immunized as above. At 3 weeks, the mice were administered 150 mg/kg of cyclophosphamide i.p. every day for 3 days. The next day, the mice were challenged i.n. with 1 × 10⁹ CFU of L. pneumophila. The mice were sacrificed 48 h post-challenge, the lungs were removed, and viable bacteria from the lung tissue were counted. (C, D) Each group of mice (n = 3/group) was immunized and administered cyclophosphamide, as described in panel B. The mice were sacrificed 16 h following the intranasal challenge and the spleens removed. The splenocytes were stimulated in vitro for 48–72 h at 37°C and the cell supernatants were collected for measurement of IFN-γ (C) and TNF-α (D). *p < 0.05 compared to naïve mice.