Induction of IL-12 or IFN-γ in the lungs of neonatal IFN-γ−/−, or IFN-γR−/− and IL-12p35−/− mice following i.n. C. muridarum challenge. Groups (n = 3–4) of 1-day-old (A) BALB/c or IFN-γ−/− mice, (B) C57BL/6, IFN-γR−/−, and IL-12p35−/− mice challenged i.n. with 100 IFU of C. muridarum. The lungs were collected at the indicated time periods and induction of IL-12 (A and B); or IFN-γ (C and D) were quantitated by ELISA. Results are expressed as mean ± SD from each animal group. *P ≤ 0.05 between C. muridarum-challenged BALB/c and IFN-γ−/− mice, C57BL/6 and IFN-γR−/−, or C57BL/6 and IL-12p35−/− mice. All results are representative of 2 independent experiments.