IL-18 expression in AMs from GM^−/− mice is severely impaired but was restored by retrovirus-mediated expression of PU.1.

(A) Primary AMs from GM^+/+, GM^−/−, and SPC-GM^+/+/GM^−/− mice were assessed for the presence of mRNA transcripts encoding IL-18 or GAPDH, as a control to demonstrate evaluation of equal amounts of total RNA, using RT-PCR as described in “Materials and methods.” Photographs of ethidium bromide–stained agarose electrophoresis gels of the PCR products are shown. Each lane represents AMs from one mouse. The experiment was repeated twice with the same results. (B) Cultured AMs were exposed to adenovirus (Adenovirus infected) or not exposed (Control) for 24 hours, and then IL-18 release into the medium was quantified by ELISA as described in “Materials and methods.” The sensitivity of detection of IL-18 was 5 pg/mL. Data represent means ± SEM; n = 3 to 6 (uninfected) or 4 to 10 (infected). Differences in IL-18 release by adenovirus-infected and uninfected MH-S and mAM$PU.1+$ cells were significant (P < .03). IL-18 release by adenovirus-infected and uninfected mAM$GFP+$ cells was not significantly different (P = .88).