FIG. 5.

Induction of IL-12 by LPS and IFN-γ. (A) IL-12 mRNA. Alveolar macrophages were cultured for 24 h with 1 μg of LPS/ml and/or 5 ng of IFN-γ/ml. IL-12 p35, IL-12 p40, and HPRT mRNAs in total RNA were measured as described in the legend to Fig. 4. The resulting values for the IL-12 subunits were normalized to HPRT and plotted as fractions of the LPS- and IFN-γ-induced expression of each subunit. Each data point represents the average of two separate experiments and ≥8 PCRs. The same results were obtained from cells cultured for 36 h. (B) IL-12 activity. IL-12 bioactivity was measured by a lymphoblast proliferation assay, and the results are expressed as the relative concentrations of IL-12 as determined by comparison of the proliferation results to a standard curve generated with porcine IL-12. Each bar represents the mean ± 1 standard deviation from four experiments. (C) Time course of IL-12 expression. Alveolar macrophages were cultured with 1 μg of LPS/ml and/or 5 ng of IFN-γ/ml for 36 h. Samples of media were assayed for IL-12 bioactivity by lymphoblast proliferation assay at the times indicated, and the results are expressed as the relative concentrations of IL-12. Each bar represents the mean ± 1 standard deviation of triplicate determinations.