Fig. 4.

Legionella replicates in presence of an induced UPR. (A and B) The UPR synergizes with L. pneumophila PAMPs to induce transcription of proinflammatory cytokines. A/J BMDMs were treated with Tp (500 nM), HKLp (effective MOI of 20), or both HKLp and Tp, for 6 h. RNA isolated from total lysates was analyzed for transcription of Il-6 or Tnf-α by qRT-PCR. Expression is plotted relative to Gapdh transcript levels. (C and D) Legionella replicates in presence of an induced UPR. A/J BMDMs, treated with Tp (500 nM), Tm (1 µg/mL), or DMSO were challenged with bacteria for 14 h at an MOI of 0.5. Infected macrophages were fixed and probed with anti-L. pneumophila (Materials and Methods). The number of bacteria/vacuoles was determined for 100 cells in each of three replicates. The percentage of vacuoles with the indicated number of bacteria is plotted. Data are the mean ± SEM of three independent experiments. Statistical analyses were performed using the unpaired t test with Welch’s correction where appropriate. *P < 0.05; **P < 0.01.