FIG. 3.
B. burgdorferi-derived RNA induces IFN profile gene transcription by BMDMs. C3H/HeJ BMDMs were treated for 6 h with 2 μg B. burgdorferi (Bb) RNA, genomic DNA, RNase A-digested B. burgdorferi RNA, DNase I-digested B. burgdorferi DNA, 0.7 μM CpG oligonucleotide, 7.4 × 106/ml live B. burgdorferi organisms, live B. burgdorferi digested with DNase I or RNase A, 5 μg/ml sonicated B. burgdorferi, or sonicate digested with DNase I or RNase A. RT-PCR transcripts are displayed as the number of copies of the gene of interest normalized to 1,000 copies of the mouse β-actin housekeeping gene. (A) B. burgdorferi RNA stimulates IFN-responsive gene transcription by BMDMs. Transcript levels for Tyki and Cxcl10 are shown. Data are depicted as the means ± SEM and are representative of two independent experiments (n = 3). Statistical significance was assessed via the two-tailed, unpaired Student t test with Welch correction. *, P < 0.05 for B. burgdorferi RNA versus medium and for B. burgdorferi RNA/RNase versus B. burgdorferi RNA. **, P < 0.01 for B. burgdorferi RNA versus medium and for B. burgdorferi RNA/RNase versus B. burgdorferi RNA. (B) B. burgdorferi-derived DNA is not a ligand for BMDM IFN profile gene induction. Transcript levels for Igtp are shown. Data are depicted as the means ± SEM and are representative of four independent experiments (n = 3). Statistical analysis was performed using one-way ANOVA with the Tukey-Kramer multiple comparisons posttest. Significant differences for stimulated samples compared to medium alone: *, P < 0.05; ***, P < 0.001. Brackets indicate that there are no significant (NS) differences between live B. burgdorferi- or sonicate-stimulated samples versus the corresponding nuclease-digested treatment groups or for B. burgdorferi genomic DNA-stimulated versus B. burgdorferi DNA/DNase-digested samples. (C) Treatment with RNase A fails to destroy the 16S rRNA content in live B. burgdorferi. Transcript levels for B. burgdorferi 16S rRNA are shown. Data are shown as the means ± SEM and are representative of two independent experiments (n = 3). Statistical significance was assessed via the two-tailed, unpaired Student t test with the Welch correction. Differences between live B. burgdorferi- or live B. burgdorferi/RNase-stimulated BMDMs and medium: **, P < 0.01. Brackets indicate that there are no significant (NS) differences (P = 0.1529) between live B. burgdorferi- and live B. burgdorferi/RNase-digested samples.