Figure 2.
Mice orally infected with the rovA mutant do not express IL-1α in PPs. (A) Reverse transcription–PCR of total RNA from the PPs of C57BL/6 mice orally infected with either wild-type Ye (1 × 107 cfu) or the rovA mutant (1 × 109 cfu) for 1, 3, or 7 days. Amplified DNA was separated on a 1.5% agarose gel and visualized with ethidium bromide staining. (B) Immunohistochemical staining of PPs from C57BL/6 mice orally infected with wild-type Ye or the rovA mutant as described above. PPs were stained with antibodies specific to IL-1α or IL-1β followed by detection with the use of tyramide signal amplification. PPs were visualized by fluorescence microscopy. (Original magnification: ×200.) The number of viable Ye in the PPs was determined by plating PP tissue extracts on Petri plates specific for Ye. Results are presented as cfu/g for the surviving mice in each group. (C) RovA will complement the defect in IL-1α expression. Peritoneal macrophages were obtained from C57BL/6 mice, activated with IFN-γ for 18 h and then cocultured with (lane 1) wild-type Ye, (lane 2) rovA mutant, or (lane 3) the rovA mutant carrying an inducible copy of the rovA gene on a plasmid for 4 h. RNA was extracted and treated as described for A.